Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$202.49	10.577%	$223.9074	$223.91	$223.90	$223.90
Purchase #2	$145.46	11.643%	$162.3959	$162.40	$162.40	$162.40
Purchase #3	$109.49	8.529%	$118.8284	$118.83	$118.85	$118.80
Purchase #4	$171.47	11.287%	$190.8238	$190.82	$190.80	$190.80
Purchase #5	$123.61	11.589%	$137.9352	$137.94	$137.95	$137.90
Purchase #6	$109.26	10.132%	$120.3302	$120.33	$120.35	$120.30
Purchase #7	$152.66	7.576%	$164.2255	$164.23	$164.25	$164.20
7 purchase totals =	$1,014.44		$1,118.4464	$1,118.46	$1,118.50	$1,118.30