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	$195.38	13.599%	$221.9497	$221.95	$221.95	$221.90
Purchase #2	$75.81	10.615%	$83.8572	$83.86	$83.85	$83.90
Purchase #3	$76.38	8.103%	$82.5691	$82.57	$82.55	$82.60
Purchase #4	$7.43	9.234%	$8.1161	$8.12	$8.10	$8.10
Purchase #5	$172.73	10.221%	$190.3847	$190.38	$190.40	$190.40
Purchase #6	$14.51	7.591%	$15.6115	$15.61	$15.60	$15.60
Purchase #7	$168.41	6.825%	$179.904	$179.90	$179.90	$179.90
7 purchase totals =	$710.65		$782.3923	$782.39	$782.35	$782.40