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	$43.76	6.799%	$46.7352	$46.74	$46.75	$46.70
Purchase #2	$132.70	5.165%	$139.554	$139.55	$139.55	$139.60
Purchase #3	$60.66	5.564%	$64.0351	$64.04	$64.05	$64.00
Purchase #4	$227.42	11.627%	$253.8621	$253.86	$253.85	$253.90
Purchase #5	$123.57	11.253%	$137.4753	$137.48	$137.50	$137.50
Purchase #6	$221.72	5.190%	$233.2273	$233.23	$233.25	$233.20
Purchase #7	$201.32	11.529%	$224.5302	$224.53	$224.55	$224.50
7 purchase totals =	$1,011.15		$1,099.4192	$1,099.43	$1,099.50	$1,099.40