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	$98.27	13.185%	$111.2269	$111.23	$111.25	$111.20
Purchase #2	$244.51	6.805%	$261.1489	$261.15	$261.15	$261.10
Purchase #3	$69.68	3.264%	$71.9544	$71.95	$71.95	$72.00
Purchase #4	$134.68	11.194%	$149.7561	$149.76	$149.75	$149.80
Purchase #5	$218.68	4.428%	$228.3632	$228.36	$228.35	$228.40
Purchase #6	$57.68	3.737%	$59.8355	$59.84	$59.85	$59.80
Purchase #7	$116.90	10.256%	$128.8893	$128.89	$128.90	$128.90
7 purchase totals =	$940.40		$1,011.1743	$1,011.18	$1,011.20	$1,011.20