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	$159.51	7.623%	$171.6694	$171.67	$171.65	$171.70
Purchase #2	$238.27	10.156%	$262.4687	$262.47	$262.45	$262.50
Purchase #3	$250.94	9.648%	$275.1507	$275.15	$275.15	$275.20
Purchase #4	$46.90	13.362%	$53.1668	$53.17	$53.15	$53.20
Purchase #5	$126.88	7.341%	$136.1943	$136.19	$136.20	$136.20
Purchase #6	$180.77	4.267%	$188.4835	$188.48	$188.50	$188.50
Purchase #7	$38.48	5.750%	$40.6926	$40.69	$40.70	$40.70
7 purchase totals =	$1,041.75		$1,127.8260	$1,127.82	$1,127.80	$1,128.00