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	$85.34	6.266%	$90.6874	$90.69	$90.70	$90.70
Purchase #2	$127.85	11.406%	$142.4326	$142.43	$142.45	$142.40
Purchase #3	$157.64	10.146%	$173.6342	$173.63	$173.65	$173.60
Purchase #4	$231.35	7.243%	$248.1067	$248.11	$248.10	$248.10
Purchase #5	$243.69	11.131%	$270.8151	$270.82	$270.80	$270.80
Purchase #6	$248.64	5.738%	$262.907	$262.91	$262.90	$262.90
Purchase #7	$243.79	11.133%	$270.9311	$270.93	$270.95	$270.90
7 purchase totals =	$1,338.30		$1,459.5141	$1,459.52	$1,459.55	$1,459.40