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	$128.69	10.453%	$142.142	$142.14	$142.15	$142.10
Purchase #2	$161.67	10.805%	$179.1384	$179.14	$179.15	$179.10
Purchase #3	$39.57	6.217%	$42.0301	$42.03	$42.05	$42.00
Purchase #4	$177.32	8.551%	$192.4826	$192.48	$192.50	$192.50
Purchase #5	$174.66	6.625%	$186.2312	$186.23	$186.25	$186.20
Purchase #6	$165.86	10.559%	$183.3732	$183.37	$183.35	$183.40
Purchase #7	$86.53	13.181%	$97.9355	$97.94	$97.95	$97.90
7 purchase totals =	$934.30		$1,023.3330	$1,023.33	$1,023.40	$1,023.20