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	$237.56	5.723%	$251.1556	$251.16	$251.15	$251.20
Purchase #2	$222.86	8.317%	$241.3953	$241.40	$241.40	$241.40
Purchase #3	$43.27	12.500%	$48.6788	$48.68	$48.70	$48.70
Purchase #4	$35.40	9.618%	$38.8048	$38.80	$38.80	$38.80
Purchase #5	$235.46	5.393%	$248.1584	$248.16	$248.15	$248.20
Purchase #6	$125.31	9.260%	$136.9137	$136.91	$136.90	$136.90
Purchase #7	$88.96	7.825%	$95.9211	$95.92	$95.90	$95.90
7 purchase totals =	$988.82		$1,061.0277	$1,061.03	$1,061.00	$1,061.10