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	$56.79	5.145%	$59.7118	$59.71	$59.70	$59.70
Purchase #2	$99.81	11.547%	$111.3351	$111.34	$111.35	$111.30
Purchase #3	$198.32	6.804%	$211.8137	$211.81	$211.80	$211.80
Purchase #4	$222.44	10.401%	$245.576	$245.58	$245.60	$245.60
Purchase #5	$138.91	4.164%	$144.6942	$144.69	$144.70	$144.70
Purchase #6	$89.82	5.817%	$95.0448	$95.04	$95.05	$95.00
Purchase #7	$93.48	3.701%	$96.9397	$96.94	$96.95	$96.90
7 purchase totals =	$899.57		$965.1153	$965.11	$965.15	$965.00