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	$32.31	6.862%	$34.5271	$34.53	$34.55	$34.50
Purchase #2	$78.58	6.217%	$83.4653	$83.47	$83.45	$83.50
Purchase #3	$31.75	8.620%	$34.4869	$34.49	$34.50	$34.50
Purchase #4	$148.33	11.378%	$165.207	$165.21	$165.20	$165.20
Purchase #5	$56.48	5.856%	$59.7875	$59.79	$59.80	$59.80
Purchase #6	$32.64	6.380%	$34.7224	$34.72	$34.70	$34.70
Purchase #7	$136.74	11.760%	$152.8206	$152.82	$152.80	$152.80
7 purchase totals =	$516.83		$565.0168	$565.03	$565.00	$565.00