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	$42.87	5.224%	$45.1095	$45.11	$45.10	$45.10
Purchase #2	$13.33	11.398%	$14.8494	$14.85	$14.85	$14.80
Purchase #3	$46.30	13.401%	$52.5047	$52.50	$52.50	$52.50
Purchase #4	$174.59	12.405%	$196.2479	$196.25	$196.25	$196.20
Purchase #5	$201.42	12.702%	$227.0044	$227.00	$227.00	$227.00
Purchase #6	$246.92	8.871%	$268.8243	$268.82	$268.80	$268.80
Purchase #7	$47.29	7.666%	$50.9153	$50.92	$50.90	$50.90
7 purchase totals =	$772.72		$855.4555	$855.45	$855.40	$855.30