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	$173.54	12.375%	$195.0156	$195.02	$195.00	$195.00
Purchase #2	$150.37	8.238%	$162.7575	$162.76	$162.75	$162.80
Purchase #3	$7.59	4.210%	$7.9095	$7.91	$7.90	$7.90
Purchase #4	$81.33	11.253%	$90.4821	$90.48	$90.50	$90.50
Purchase #5	$100.47	10.228%	$110.7461	$110.75	$110.75	$110.70
Purchase #6	$18.69	12.589%	$21.0429	$21.04	$21.05	$21.00
Purchase #7	$222.46	13.865%	$253.3041	$253.30	$253.30	$253.30
7 purchase totals =	$754.45		$841.2578	$841.26	$841.25	$841.20