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	$88.33	8.413%	$95.7612	$95.76	$95.75	$95.80
Purchase #2	$40.29	4.499%	$42.1026	$42.10	$42.10	$42.10
Purchase #3	$52.52	3.600%	$54.4107	$54.41	$54.40	$54.40
Purchase #4	$50.42	7.620%	$54.262	$54.26	$54.25	$54.30
Purchase #5	$44.80	9.197%	$48.9203	$48.92	$48.90	$48.90
Purchase #6	$230.68	11.650%	$257.5542	$257.55	$257.55	$257.60
Purchase #7	$113.39	11.374%	$126.287	$126.29	$126.30	$126.30
7 purchase totals =	$620.43		$679.2980	$679.29	$679.25	$679.40