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	$165.31	12.589%	$186.1209	$186.12	$186.10	$186.10
Purchase #2	$56.95	3.763%	$59.093	$59.09	$59.10	$59.10
Purchase #3	$149.36	6.146%	$158.5397	$158.54	$158.55	$158.50
Purchase #4	$220.99	12.401%	$248.395	$248.40	$248.40	$248.40
Purchase #5	$222.86	7.289%	$239.1043	$239.10	$239.10	$239.10
Purchase #6	$80.62	12.690%	$90.8507	$90.85	$90.85	$90.90
Purchase #7	$223.89	11.738%	$250.1702	$250.17	$250.15	$250.20
7 purchase totals =	$1,119.98		$1,232.2738	$1,232.27	$1,232.25	$1,232.30