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	$153.98	12.213%	$172.7856	$172.79	$172.80	$172.80
Purchase #2	$38.41	12.217%	$43.1025	$43.10	$43.10	$43.10
Purchase #3	$12.46	11.484%	$13.8909	$13.89	$13.90	$13.90
Purchase #4	$80.95	12.414%	$90.9991	$91.00	$91.00	$91.00
Purchase #5	$103.43	10.849%	$114.6511	$114.65	$114.65	$114.70
Purchase #6	$101.86	4.284%	$106.2237	$106.22	$106.20	$106.20
Purchase #7	$173.43	10.664%	$191.9246	$191.92	$191.90	$191.90
7 purchase totals =	$664.52		$733.5775	$733.57	$733.55	$733.60