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	$185.40	5.446%	$195.4969	$195.50	$195.50	$195.50
Purchase #2	$12.31	10.619%	$13.6172	$13.62	$13.60	$13.60
Purchase #3	$195.70	13.743%	$222.5951	$222.60	$222.60	$222.60
Purchase #4	$60.25	12.111%	$67.5469	$67.55	$67.55	$67.50
Purchase #5	$42.73	13.373%	$48.4443	$48.44	$48.45	$48.40
Purchase #6	$92.47	9.418%	$101.1788	$101.18	$101.20	$101.20
Purchase #7	$19.93	13.867%	$22.6937	$22.69	$22.70	$22.70
7 purchase totals =	$608.79		$671.5729	$671.58	$671.60	$671.50