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	$99.31	11.865%	$111.0931	$111.09	$111.10	$111.10
Purchase #2	$42.71	11.511%	$47.6263	$47.63	$47.65	$47.60
Purchase #3	$240.25	4.168%	$250.2636	$250.26	$250.25	$250.30
Purchase #4	$106.51	11.757%	$119.0324	$119.03	$119.05	$119.00
Purchase #5	$111.30	13.607%	$126.4446	$126.44	$126.45	$126.40
Purchase #6	$141.65	9.673%	$155.3518	$155.35	$155.35	$155.40
Purchase #7	$234.94	3.588%	$243.3696	$243.37	$243.35	$243.40
7 purchase totals =	$976.67		$1,053.1814	$1,053.17	$1,053.20	$1,053.20