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	$209.91	7.291%	$225.2145	$225.21	$225.20	$225.20
Purchase #2	$42.56	5.777%	$45.0187	$45.02	$45.00	$45.00
Purchase #3	$70.34	3.575%	$72.8547	$72.85	$72.85	$72.90
Purchase #4	$23.40	8.261%	$25.3331	$25.33	$25.35	$25.30
Purchase #5	$109.58	8.246%	$118.616	$118.62	$118.60	$118.60
Purchase #6	$55.38	8.224%	$59.9345	$59.93	$59.95	$59.90
Purchase #7	$68.74	13.504%	$78.0226	$78.02	$78.00	$78.00
7 purchase totals =	$579.91		$624.9941	$624.98	$624.95	$624.90