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	$157.87	10.676%	$174.7242	$174.72	$174.70	$174.70
Purchase #2	$186.61	13.154%	$211.1567	$211.16	$211.15	$211.20
Purchase #3	$37.85	9.771%	$41.5483	$41.55	$41.55	$41.50
Purchase #4	$40.75	11.618%	$45.4843	$45.48	$45.50	$45.50
Purchase #5	$130.85	4.313%	$136.4936	$136.49	$136.50	$136.50
Purchase #6	$182.76	9.857%	$200.7747	$200.77	$200.75	$200.80
Purchase #7	$139.90	13.555%	$158.8634	$158.86	$158.85	$158.90
7 purchase totals =	$876.59		$969.0452	$969.03	$969.00	$969.10