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	$55.42	12.132%	$62.1436	$62.14	$62.15	$62.10
Purchase #2	$37.42	5.112%	$39.3329	$39.33	$39.35	$39.30
Purchase #3	$46.46	12.749%	$52.3832	$52.38	$52.40	$52.40
Purchase #4	$11.91	10.795%	$13.1957	$13.20	$13.20	$13.20
Purchase #5	$79.31	12.818%	$89.476	$89.48	$89.50	$89.50
Purchase #6	$107.73	3.186%	$111.1623	$111.16	$111.15	$111.20
Purchase #7	$171.53	8.137%	$185.4874	$185.49	$185.50	$185.50
7 purchase totals =	$509.78		$553.1811	$553.18	$553.25	$553.20