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	$175.27	4.262%	$182.74	$182.74	$182.75	$182.70
Purchase #2	$115.71	13.481%	$131.3089	$131.31	$131.30	$131.30
Purchase #3	$216.29	6.125%	$229.5378	$229.54	$229.55	$229.50
Purchase #4	$11.78	13.694%	$13.3932	$13.39	$13.40	$13.40
Purchase #5	$68.53	5.250%	$72.1278	$72.13	$72.15	$72.10
Purchase #6	$128.43	4.785%	$134.5754	$134.58	$134.60	$134.60
Purchase #7	$111.77	7.375%	$120.013	$120.01	$120.00	$120.00
7 purchase totals =	$827.78		$883.6961	$883.70	$883.75	$883.60