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	$37.73	10.598%	$41.7286	$41.73	$41.75	$41.70
Purchase #2	$207.88	6.743%	$221.8973	$221.90	$221.90	$221.90
Purchase #3	$133.53	3.677%	$138.4399	$138.44	$138.45	$138.40
Purchase #4	$248.69	12.325%	$279.341	$279.34	$279.35	$279.30
Purchase #5	$152.62	6.693%	$162.8349	$162.83	$162.85	$162.80
Purchase #6	$200.86	10.105%	$221.1569	$221.16	$221.15	$221.20
Purchase #7	$211.98	10.753%	$234.7742	$234.77	$234.75	$234.80
7 purchase totals =	$1,193.29		$1,300.1728	$1,300.17	$1,300.20	$1,300.10