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	$194.39	3.300%	$200.8049	$200.80	$200.80	$200.80
Purchase #2	$175.25	5.107%	$184.2	$184.20	$184.20	$184.20
Purchase #3	$223.77	3.243%	$231.0269	$231.03	$231.05	$231.00
Purchase #4	$244.41	10.106%	$269.1101	$269.11	$269.10	$269.10
Purchase #5	$165.35	10.220%	$182.2488	$182.25	$182.25	$182.20
Purchase #6	$89.58	9.539%	$98.125	$98.13	$98.15	$98.10
Purchase #7	$87.82	13.269%	$99.4728	$99.47	$99.45	$99.50
7 purchase totals =	$1,180.57		$1,264.9885	$1,264.99	$1,265.00	$1,264.90