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	$229.41	7.175%	$245.8702	$245.87	$245.85	$245.90
Purchase #2	$169.47	12.360%	$190.4165	$190.42	$190.40	$190.40
Purchase #3	$105.47	11.196%	$117.2784	$117.28	$117.30	$117.30
Purchase #4	$240.72	4.560%	$251.6968	$251.70	$251.70	$251.70
Purchase #5	$37.50	10.874%	$41.5778	$41.58	$41.60	$41.60
Purchase #6	$174.92	10.854%	$193.9058	$193.91	$193.90	$193.90
Purchase #7	$72.60	7.650%	$78.1539	$78.15	$78.15	$78.20
7 purchase totals =	$1,030.09		$1,118.8994	$1,118.91	$1,118.90	$1,119.00