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	$7.50	5.673%	$7.9255	$7.93	$7.95	$7.90
Purchase #2	$10.55	11.188%	$11.7303	$11.73	$11.75	$11.70
Purchase #3	$127.57	4.678%	$133.5377	$133.54	$133.55	$133.50
Purchase #4	$197.69	7.617%	$212.748	$212.75	$212.75	$212.70
Purchase #5	$247.52	8.319%	$268.1112	$268.11	$268.10	$268.10
Purchase #6	$81.34	9.519%	$89.0828	$89.08	$89.10	$89.10
Purchase #7	$101.39	9.516%	$111.0383	$111.04	$111.05	$111.00
7 purchase totals =	$773.56		$834.1738	$834.18	$834.25	$834.00