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	$33.69	6.625%	$35.922	$35.92	$35.90	$35.90
Purchase #2	$10.51	9.606%	$11.5196	$11.52	$11.50	$11.50
Purchase #3	$67.27	8.391%	$72.9146	$72.91	$72.90	$72.90
Purchase #4	$200.32	8.597%	$217.5415	$217.54	$217.55	$217.50
Purchase #5	$222.98	9.349%	$243.8264	$243.83	$243.85	$243.80
Purchase #6	$232.46	8.330%	$251.8239	$251.82	$251.80	$251.80
Purchase #7	$105.91	11.392%	$117.9753	$117.98	$118.00	$118.00
7 purchase totals =	$873.14		$951.5233	$951.52	$951.50	$951.40