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	$172.57	10.834%	$191.2662	$191.27	$191.25	$191.30
Purchase #2	$214.68	13.399%	$243.445	$243.45	$243.45	$243.40
Purchase #3	$70.33	9.401%	$76.9417	$76.94	$76.95	$76.90
Purchase #4	$221.31	5.397%	$233.2541	$233.25	$233.25	$233.30
Purchase #5	$11.43	11.361%	$12.7286	$12.73	$12.75	$12.70
Purchase #6	$216.63	3.131%	$223.4127	$223.41	$223.40	$223.40
Purchase #7	$27.63	12.220%	$31.0064	$31.01	$31.00	$31.00
7 purchase totals =	$934.58		$1,012.0547	$1,012.06	$1,012.05	$1,012.00