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	$40.72	12.479%	$45.8014	$45.80	$45.80	$45.80
Purchase #2	$243.57	12.672%	$274.4352	$274.44	$274.45	$274.40
Purchase #3	$69.56	13.662%	$79.0633	$79.06	$79.05	$79.10
Purchase #4	$131.36	11.662%	$146.6792	$146.68	$146.70	$146.70
Purchase #5	$94.90	11.635%	$105.9416	$105.94	$105.95	$105.90
Purchase #6	$219.47	4.113%	$228.4968	$228.50	$228.50	$228.50
Purchase #7	$118.88	11.265%	$132.2718	$132.27	$132.25	$132.30
7 purchase totals =	$918.46		$1,012.6893	$1,012.69	$1,012.70	$1,012.70