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	$212.95	6.112%	$225.9655	$225.97	$225.95	$226.00
Purchase #2	$128.28	12.381%	$144.1623	$144.16	$144.15	$144.20
Purchase #3	$246.73	7.479%	$265.1829	$265.18	$265.20	$265.20
Purchase #4	$62.70	10.277%	$69.1437	$69.14	$69.15	$69.10
Purchase #5	$51.37	5.838%	$54.369	$54.37	$54.35	$54.40
Purchase #6	$37.31	9.687%	$40.9242	$40.92	$40.90	$40.90
Purchase #7	$75.96	12.635%	$85.5575	$85.56	$85.55	$85.60
7 purchase totals =	$815.30		$885.3051	$885.30	$885.25	$885.40