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	9.427%	$94.4683	$94.47	$94.45	$94.50
Purchase #2	$171.57	11.651%	$191.5596	$191.56	$191.55	$191.60
Purchase #3	$64.64	4.322%	$67.4337	$67.43	$67.45	$67.40
Purchase #4	$106.86	4.781%	$111.969	$111.97	$111.95	$112.00
Purchase #5	$88.41	9.428%	$96.7453	$96.75	$96.75	$96.70
Purchase #6	$61.97	8.581%	$67.2876	$67.29	$67.30	$67.30
Purchase #7	$69.65	9.452%	$76.2333	$76.23	$76.25	$76.20
7 purchase totals =	$649.43		$705.6968	$705.70	$705.70	$705.70