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	$186.89	5.160%	$196.5335	$196.53	$196.55	$196.50
Purchase #2	$188.90	5.516%	$199.3197	$199.32	$199.30	$199.30
Purchase #3	$127.34	10.553%	$140.7782	$140.78	$140.80	$140.80
Purchase #4	$236.91	12.770%	$267.1634	$267.16	$267.15	$267.20
Purchase #5	$231.41	12.205%	$259.6536	$259.65	$259.65	$259.70
Purchase #6	$213.81	7.707%	$230.2883	$230.29	$230.30	$230.30
Purchase #7	$70.86	10.439%	$78.2571	$78.26	$78.25	$78.30
7 purchase totals =	$1,256.12		$1,371.9938	$1,371.99	$1,372.00	$1,372.10