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	$152.38	12.234%	$171.0222	$171.02	$171.00	$171.00
Purchase #2	$227.49	11.746%	$254.211	$254.21	$254.20	$254.20
Purchase #3	$150.26	9.687%	$164.8157	$164.82	$164.80	$164.80
Purchase #4	$167.75	7.584%	$180.4722	$180.47	$180.45	$180.50
Purchase #5	$122.56	3.510%	$126.8619	$126.86	$126.85	$126.90
Purchase #6	$148.44	3.837%	$154.1356	$154.14	$154.15	$154.10
Purchase #7	$67.28	13.535%	$76.3863	$76.39	$76.40	$76.40
7 purchase totals =	$1,036.16		$1,127.9049	$1,127.91	$1,127.85	$1,127.90