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	$161.52	11.104%	$179.4552	$179.46	$179.45	$179.50
Purchase #2	$219.86	10.786%	$243.5741	$243.57	$243.55	$243.60
Purchase #3	$71.63	7.568%	$77.051	$77.05	$77.05	$77.10
Purchase #4	$139.40	8.859%	$151.7494	$151.75	$151.75	$151.70
Purchase #5	$237.34	13.539%	$269.4735	$269.47	$269.45	$269.50
Purchase #6	$126.41	13.388%	$143.3338	$143.33	$143.35	$143.30
Purchase #7	$135.77	7.153%	$145.4816	$145.48	$145.50	$145.50
7 purchase totals =	$1,091.93		$1,210.1186	$1,210.11	$1,210.10	$1,210.20