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	$198.57	3.449%	$205.4187	$205.42	$205.40	$205.40
Purchase #2	$223.39	7.615%	$240.4011	$240.40	$240.40	$240.40
Purchase #3	$195.44	9.220%	$213.4596	$213.46	$213.45	$213.50
Purchase #4	$18.98	7.329%	$20.371	$20.37	$20.35	$20.40
Purchase #5	$173.51	12.311%	$194.8708	$194.87	$194.85	$194.90
Purchase #6	$191.41	4.244%	$199.5334	$199.53	$199.55	$199.50
Purchase #7	$164.89	8.830%	$179.4498	$179.45	$179.45	$179.40
7 purchase totals =	$1,166.19		$1,253.5044	$1,253.50	$1,253.45	$1,253.50