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	$55.83	5.181%	$58.7226	$58.72	$58.70	$58.70
Purchase #2	$48.45	9.551%	$53.0775	$53.08	$53.10	$53.10
Purchase #3	$100.56	13.541%	$114.1768	$114.18	$114.20	$114.20
Purchase #4	$10.75	9.136%	$11.7321	$11.73	$11.75	$11.70
Purchase #5	$16.83	9.816%	$18.482	$18.48	$18.50	$18.50
Purchase #6	$36.83	11.704%	$41.1406	$41.14	$41.15	$41.10
Purchase #7	$131.96	12.774%	$148.8166	$148.82	$148.80	$148.80
7 purchase totals =	$401.21		$446.1482	$446.15	$446.20	$446.10