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	$47.71	12.468%	$53.6585	$53.66	$53.65	$53.70
Purchase #2	$245.51	5.781%	$259.7029	$259.70	$259.70	$259.70
Purchase #3	$20.82	5.388%	$21.9418	$21.94	$21.95	$21.90
Purchase #4	$164.62	10.302%	$181.5792	$181.58	$181.60	$181.60
Purchase #5	$155.55	7.764%	$167.6269	$167.63	$167.65	$167.60
Purchase #6	$175.95	8.829%	$191.4846	$191.48	$191.50	$191.50
Purchase #7	$160.50	6.729%	$171.3	$171.30	$171.30	$171.30
7 purchase totals =	$970.66		$1,047.2939	$1,047.29	$1,047.35	$1,047.30