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	$223.47	12.377%	$251.1289	$251.13	$251.15	$251.10
Purchase #2	$164.68	4.546%	$172.1664	$172.17	$172.15	$172.20
Purchase #3	$211.86	6.421%	$225.4635	$225.46	$225.45	$225.50
Purchase #4	$81.80	10.437%	$90.3375	$90.34	$90.35	$90.30
Purchase #5	$182.27	7.410%	$195.7762	$195.78	$195.80	$195.80
Purchase #6	$235.74	9.793%	$258.826	$258.83	$258.85	$258.80
Purchase #7	$56.71	8.247%	$61.3869	$61.39	$61.40	$61.40
7 purchase totals =	$1,156.53		$1,255.0854	$1,255.10	$1,255.15	$1,255.10