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	$59.89	3.179%	$61.7939	$61.79	$61.80	$61.80
Purchase #2	$101.27	3.533%	$104.8479	$104.85	$104.85	$104.80
Purchase #3	$34.29	8.478%	$37.1971	$37.20	$37.20	$37.20
Purchase #4	$62.75	3.548%	$64.9764	$64.98	$65.00	$65.00
Purchase #5	$235.83	6.505%	$251.1707	$251.17	$251.15	$251.20
Purchase #6	$205.69	13.463%	$233.382	$233.38	$233.40	$233.40
Purchase #7	$248.46	6.767%	$265.2733	$265.27	$265.25	$265.30
7 purchase totals =	$948.18		$1,018.6413	$1,018.64	$1,018.65	$1,018.70