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	$232.98	8.119%	$251.8956	$251.90	$251.90	$251.90
Purchase #2	$151.83	10.808%	$168.2398	$168.24	$168.25	$168.20
Purchase #3	$88.27	13.588%	$100.2641	$100.26	$100.25	$100.30
Purchase #4	$89.66	10.211%	$98.8152	$98.82	$98.80	$98.80
Purchase #5	$20.99	4.243%	$21.8806	$21.88	$21.90	$21.90
Purchase #6	$241.50	7.637%	$259.9434	$259.94	$259.95	$259.90
Purchase #7	$231.67	6.709%	$247.2127	$247.21	$247.20	$247.20
7 purchase totals =	$1,056.90		$1,148.2514	$1,148.25	$1,148.25	$1,148.20