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	$57.95	3.683%	$60.0843	$60.08	$60.10	$60.10
Purchase #2	$31.47	4.561%	$32.9053	$32.91	$32.90	$32.90
Purchase #3	$48.98	11.465%	$54.5956	$54.60	$54.60	$54.60
Purchase #4	$199.62	4.555%	$208.7127	$208.71	$208.70	$208.70
Purchase #5	$36.69	6.355%	$39.0216	$39.02	$39.00	$39.00
Purchase #6	$218.91	5.851%	$231.7184	$231.72	$231.70	$231.70
Purchase #7	$32.83	3.175%	$33.8724	$33.87	$33.85	$33.90
7 purchase totals =	$626.45		$660.9103	$660.91	$660.85	$660.90