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	$126.58	11.578%	$141.2354	$141.24	$141.25	$141.20
Purchase #2	$100.33	10.843%	$111.2088	$111.21	$111.20	$111.20
Purchase #3	$52.51	12.529%	$59.089	$59.09	$59.10	$59.10
Purchase #4	$33.99	3.258%	$35.0974	$35.10	$35.10	$35.10
Purchase #5	$222.57	9.503%	$243.7208	$243.72	$243.70	$243.70
Purchase #6	$219.30	13.229%	$248.3112	$248.31	$248.30	$248.30
Purchase #7	$145.81	13.189%	$165.0409	$165.04	$165.05	$165.00
7 purchase totals =	$901.09		$1,003.7035	$1,003.71	$1,003.70	$1,003.60