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	$85.71	7.154%	$91.8417	$91.84	$91.85	$91.80
Purchase #2	$119.72	12.680%	$134.9005	$134.90	$134.90	$134.90
Purchase #3	$199.56	9.551%	$218.62	$218.62	$218.60	$218.60
Purchase #4	$52.99	5.220%	$55.7561	$55.76	$55.75	$55.80
Purchase #5	$54.89	7.795%	$59.1687	$59.17	$59.15	$59.20
Purchase #6	$111.40	4.386%	$116.286	$116.29	$116.30	$116.30
Purchase #7	$60.57	6.105%	$64.2678	$64.27	$64.25	$64.30
7 purchase totals =	$684.84		$740.8408	$740.85	$740.80	$740.90