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	$191.29	10.266%	$210.9278	$210.93	$210.95	$210.90
Purchase #2	$129.87	11.491%	$144.7934	$144.79	$144.80	$144.80
Purchase #3	$174.89	4.150%	$182.1479	$182.15	$182.15	$182.10
Purchase #4	$35.54	6.514%	$37.8551	$37.86	$37.85	$37.90
Purchase #5	$40.40	6.830%	$43.1593	$43.16	$43.15	$43.20
Purchase #6	$239.84	13.642%	$272.559	$272.56	$272.55	$272.60
Purchase #7	$152.69	8.375%	$165.4778	$165.48	$165.50	$165.50
7 purchase totals =	$964.52		$1,056.9203	$1,056.93	$1,056.95	$1,057.00