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	$195.62	13.727%	$222.4728	$222.47	$222.45	$222.50
Purchase #2	$168.58	11.531%	$188.019	$188.02	$188.00	$188.00
Purchase #3	$172.74	6.579%	$184.1046	$184.10	$184.10	$184.10
Purchase #4	$250.43	11.478%	$279.1744	$279.17	$279.15	$279.20
Purchase #5	$71.48	9.815%	$78.4958	$78.50	$78.50	$78.50
Purchase #6	$119.90	3.688%	$124.3219	$124.32	$124.30	$124.30
Purchase #7	$160.50	11.864%	$179.5417	$179.54	$179.55	$179.50
7 purchase totals =	$1,139.25		$1,256.1302	$1,256.12	$1,256.05	$1,256.10