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	$56.40	5.624%	$59.5719	$59.57	$59.55	$59.60
Purchase #2	$63.51	13.636%	$72.1702	$72.17	$72.15	$72.20
Purchase #3	$101.25	9.327%	$110.6936	$110.69	$110.70	$110.70
Purchase #4	$60.43	11.630%	$67.458	$67.46	$67.45	$67.50
Purchase #5	$243.39	8.398%	$263.8299	$263.83	$263.85	$263.80
Purchase #6	$152.35	13.337%	$172.6689	$172.67	$172.65	$172.70
Purchase #7	$37.63	3.551%	$38.9662	$38.97	$38.95	$39.00
7 purchase totals =	$714.96		$785.3587	$785.36	$785.30	$785.50