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	$59.84	12.489%	$67.3134	$67.31	$67.30	$67.30
Purchase #2	$175.61	8.531%	$190.5913	$190.59	$190.60	$190.60
Purchase #3	$48.55	9.843%	$53.3288	$53.33	$53.35	$53.30
Purchase #4	$135.58	6.356%	$144.1975	$144.20	$144.20	$144.20
Purchase #5	$5.67	13.861%	$6.4559	$6.46	$6.45	$6.50
Purchase #6	$193.34	6.158%	$205.2459	$205.25	$205.25	$205.20
Purchase #7	$79.39	7.666%	$85.476	$85.48	$85.50	$85.50
7 purchase totals =	$697.98		$752.6088	$752.62	$752.65	$752.60