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	$213.66	8.555%	$231.9386	$231.94	$231.95	$231.90
Purchase #2	$18.58	4.385%	$19.3947	$19.39	$19.40	$19.40
Purchase #3	$30.89	3.154%	$31.8643	$31.86	$31.85	$31.90
Purchase #4	$147.98	11.805%	$165.449	$165.45	$165.45	$165.40
Purchase #5	$42.53	6.120%	$45.1328	$45.13	$45.15	$45.10
Purchase #6	$111.74	3.262%	$115.385	$115.39	$115.40	$115.40
Purchase #7	$195.94	5.283%	$206.2915	$206.29	$206.30	$206.30
7 purchase totals =	$761.32		$815.4559	$815.45	$815.50	$815.40