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	$86.33	6.719%	$92.1305	$92.13	$92.15	$92.10
Purchase #2	$233.43	11.689%	$260.7156	$260.72	$260.70	$260.70
Purchase #3	$148.82	4.238%	$155.127	$155.13	$155.15	$155.10
Purchase #4	$235.27	8.157%	$254.461	$254.46	$254.45	$254.50
Purchase #5	$234.96	3.395%	$242.9369	$242.94	$242.95	$242.90
Purchase #6	$208.89	3.128%	$215.4241	$215.42	$215.40	$215.40
Purchase #7	$88.89	7.296%	$95.3754	$95.38	$95.40	$95.40
7 purchase totals =	$1,236.59		$1,316.1705	$1,316.18	$1,316.20	$1,316.10