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	$206.37	8.490%	$223.8908	$223.89	$223.90	$223.90
Purchase #2	$133.30	4.685%	$139.5451	$139.55	$139.55	$139.50
Purchase #3	$164.94	5.596%	$174.17	$174.17	$174.15	$174.20
Purchase #4	$93.95	6.779%	$100.3189	$100.32	$100.30	$100.30
Purchase #5	$33.74	9.758%	$37.0323	$37.03	$37.05	$37.00
Purchase #6	$93.80	11.232%	$104.3356	$104.34	$104.35	$104.30
Purchase #7	$190.34	6.220%	$202.1791	$202.18	$202.20	$202.20
7 purchase totals =	$916.44		$981.4718	$981.48	$981.50	$981.40