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	$52.58	10.226%	$57.9568	$57.96	$57.95	$58.00
Purchase #2	$59.28	8.444%	$64.2856	$64.29	$64.30	$64.30
Purchase #3	$57.26	8.186%	$61.9473	$61.95	$61.95	$61.90
Purchase #4	$214.30	10.192%	$236.1415	$236.14	$236.15	$236.10
Purchase #5	$128.96	10.309%	$142.2545	$142.25	$142.25	$142.30
Purchase #6	$119.55	7.265%	$128.2353	$128.24	$128.25	$128.20
Purchase #7	$98.95	12.244%	$111.0654	$111.07	$111.05	$111.10
7 purchase totals =	$730.88		$801.8864	$801.90	$801.90	$801.90