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	$196.51	6.663%	$209.6035	$209.60	$209.60	$209.60
Purchase #2	$19.75	3.873%	$20.5149	$20.51	$20.50	$20.50
Purchase #3	$135.79	3.438%	$140.4585	$140.46	$140.45	$140.50
Purchase #4	$86.28	10.447%	$95.2937	$95.29	$95.30	$95.30
Purchase #5	$216.57	8.788%	$235.6022	$235.60	$235.60	$235.60
Purchase #6	$105.77	5.814%	$111.9195	$111.92	$111.90	$111.90
Purchase #7	$71.53	8.821%	$77.8397	$77.84	$77.85	$77.80
7 purchase totals =	$832.20		$891.2320	$891.22	$891.20	$891.20