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	$99.74	12.636%	$112.3431	$112.34	$112.35	$112.30
Purchase #2	$85.89	7.543%	$92.3687	$92.37	$92.35	$92.40
Purchase #3	$187.28	10.408%	$206.7721	$206.77	$206.75	$206.80
Purchase #4	$130.37	6.672%	$139.0683	$139.07	$139.05	$139.10
Purchase #5	$5.48	12.328%	$6.1556	$6.16	$6.15	$6.20
Purchase #6	$229.83	11.170%	$255.502	$255.50	$255.50	$255.50
Purchase #7	$201.74	5.490%	$212.8155	$212.82	$212.80	$212.80
7 purchase totals =	$940.33		$1,025.0253	$1,025.03	$1,024.95	$1,025.10