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	$198.37	12.214%	$222.5989	$222.60	$222.60	$222.60
Purchase #2	$20.30	11.618%	$22.6585	$22.66	$22.65	$22.70
Purchase #3	$99.93	11.219%	$111.1411	$111.14	$111.15	$111.10
Purchase #4	$197.69	7.843%	$213.1948	$213.19	$213.20	$213.20
Purchase #5	$219.59	4.695%	$229.8998	$229.90	$229.90	$229.90
Purchase #6	$233.66	6.684%	$249.2778	$249.28	$249.30	$249.30
Purchase #7	$55.98	3.338%	$57.8486	$57.85	$57.85	$57.80
7 purchase totals =	$1,025.52		$1,106.6195	$1,106.62	$1,106.65	$1,106.60