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	$143.32	6.659%	$152.8637	$152.86	$152.85	$152.90
Purchase #2	$40.63	6.188%	$43.1442	$43.14	$43.15	$43.10
Purchase #3	$51.46	7.289%	$55.2109	$55.21	$55.20	$55.20
Purchase #4	$18.55	13.491%	$21.0526	$21.05	$21.05	$21.10
Purchase #5	$102.51	8.454%	$111.1762	$111.18	$111.20	$111.20
Purchase #6	$84.55	9.113%	$92.255	$92.26	$92.25	$92.30
Purchase #7	$232.61	4.708%	$243.5613	$243.56	$243.55	$243.60
7 purchase totals =	$673.63		$719.2639	$719.26	$719.25	$719.40