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	$243.47	10.676%	$269.4629	$269.46	$269.45	$269.50
Purchase #2	$132.67	12.757%	$149.5947	$149.59	$149.60	$149.60
Purchase #3	$242.31	9.601%	$265.5742	$265.57	$265.55	$265.60
Purchase #4	$127.33	4.800%	$133.4418	$133.44	$133.45	$133.40
Purchase #5	$209.47	11.373%	$233.293	$233.29	$233.30	$233.30
Purchase #6	$173.56	13.465%	$196.9299	$196.93	$196.95	$196.90
Purchase #7	$73.90	10.442%	$81.6166	$81.62	$81.60	$81.60
7 purchase totals =	$1,202.71		$1,329.9131	$1,329.90	$1,329.90	$1,329.90