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	$104.88	8.854%	$114.1661	$114.17	$114.15	$114.20
Purchase #2	$112.92	9.250%	$123.3651	$123.37	$123.35	$123.40
Purchase #3	$39.64	12.188%	$44.4713	$44.47	$44.45	$44.50
Purchase #4	$149.85	10.184%	$165.1107	$165.11	$165.10	$165.10
Purchase #5	$147.45	5.741%	$155.9151	$155.92	$155.90	$155.90
Purchase #6	$223.38	11.203%	$248.4053	$248.41	$248.40	$248.40
Purchase #7	$136.84	4.874%	$143.5096	$143.51	$143.50	$143.50
7 purchase totals =	$914.96		$994.9432	$994.96	$994.85	$995.00