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	$49.43	6.153%	$52.4714	$52.47	$52.45	$52.50
Purchase #2	$185.50	7.750%	$199.8763	$199.88	$199.90	$199.90
Purchase #3	$126.25	13.783%	$143.651	$143.65	$143.65	$143.70
Purchase #4	$54.40	13.604%	$61.8006	$61.80	$61.80	$61.80
Purchase #5	$40.82	3.791%	$42.3675	$42.37	$42.35	$42.40
Purchase #6	$237.51	13.225%	$268.9207	$268.92	$268.90	$268.90
Purchase #7	$203.43	10.689%	$225.1746	$225.17	$225.15	$225.20
7 purchase totals =	$897.34		$994.2621	$994.26	$994.20	$994.40