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	$65.57	11.170%	$72.8942	$72.89	$72.90	$72.90
Purchase #2	$140.74	10.451%	$155.4487	$155.45	$155.45	$155.40
Purchase #3	$30.49	9.372%	$33.3475	$33.35	$33.35	$33.30
Purchase #4	$86.37	5.604%	$91.2102	$91.21	$91.20	$91.20
Purchase #5	$177.63	12.325%	$199.5229	$199.52	$199.50	$199.50
Purchase #6	$99.61	9.497%	$109.07	$109.07	$109.05	$109.10
Purchase #7	$64.47	11.648%	$71.9795	$71.98	$72.00	$72.00
7 purchase totals =	$664.88		$733.4730	$733.47	$733.45	$733.40