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	$31.81	3.434%	$32.9024	$32.90	$32.90	$32.90
Purchase #2	$30.28	7.737%	$32.6228	$32.62	$32.60	$32.60
Purchase #3	$237.27	5.164%	$249.5226	$249.52	$249.50	$249.50
Purchase #4	$82.64	11.322%	$91.9965	$92.00	$92.00	$92.00
Purchase #5	$72.27	12.379%	$81.2163	$81.22	$81.20	$81.20
Purchase #6	$59.54	12.643%	$67.0676	$67.07	$67.05	$67.10
Purchase #7	$74.89	3.709%	$77.6677	$77.67	$77.65	$77.70
7 purchase totals =	$588.70		$632.9959	$633.00	$632.90	$633.00