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	$70.49	10.821%	$78.1177	$78.12	$78.10	$78.10
Purchase #2	$157.71	5.448%	$166.302	$166.30	$166.30	$166.30
Purchase #3	$76.61	11.149%	$85.1512	$85.15	$85.15	$85.20
Purchase #4	$25.66	6.206%	$27.2525	$27.25	$27.25	$27.30
Purchase #5	$53.31	7.454%	$57.2837	$57.28	$57.30	$57.30
Purchase #6	$68.78	11.278%	$76.537	$76.54	$76.55	$76.50
Purchase #7	$244.52	4.754%	$256.1445	$256.14	$256.15	$256.10
7 purchase totals =	$697.08		$746.7886	$746.78	$746.80	$746.80