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	$31.89	5.139%	$33.5288	$33.53	$33.55	$33.50
Purchase #2	$182.89	12.808%	$206.3146	$206.31	$206.30	$206.30
Purchase #3	$33.25	11.328%	$37.0166	$37.02	$37.00	$37.00
Purchase #4	$52.36	13.553%	$59.4564	$59.46	$59.45	$59.50
Purchase #5	$71.69	5.161%	$75.3899	$75.39	$75.40	$75.40
Purchase #6	$103.33	7.508%	$111.088	$111.09	$111.10	$111.10
Purchase #7	$236.28	13.162%	$267.3792	$267.38	$267.40	$267.40
7 purchase totals =	$711.69		$790.1735	$790.18	$790.20	$790.20