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	$211.34	8.389%	$229.0693	$229.07	$229.05	$229.10
Purchase #2	$230.45	9.822%	$253.0848	$253.08	$253.10	$253.10
Purchase #3	$90.37	5.484%	$95.3259	$95.33	$95.35	$95.30
Purchase #4	$100.25	3.652%	$103.9111	$103.91	$103.90	$103.90
Purchase #5	$84.35	5.762%	$89.2102	$89.21	$89.20	$89.20
Purchase #6	$9.63	6.227%	$10.2297	$10.23	$10.25	$10.20
Purchase #7	$222.38	12.638%	$250.4844	$250.48	$250.50	$250.50
7 purchase totals =	$948.77		$1,031.3154	$1,031.31	$1,031.35	$1,031.30