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	$37.64	10.667%	$41.6551	$41.66	$41.65	$41.70
Purchase #2	$74.66	4.426%	$77.9645	$77.96	$77.95	$78.00
Purchase #3	$44.28	11.717%	$49.4683	$49.47	$49.45	$49.50
Purchase #4	$245.25	4.124%	$255.3641	$255.36	$255.35	$255.40
Purchase #5	$147.70	3.123%	$152.3127	$152.31	$152.30	$152.30
Purchase #6	$131.43	8.708%	$142.8749	$142.87	$142.85	$142.90
Purchase #7	$136.63	13.568%	$155.168	$155.17	$155.15	$155.20
7 purchase totals =	$817.59		$874.8076	$874.80	$874.70	$875.00