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	$234.43	13.581%	$266.2679	$266.27	$266.25	$266.30
Purchase #2	$111.70	11.190%	$124.1992	$124.20	$124.20	$124.20
Purchase #3	$146.61	6.221%	$155.7306	$155.73	$155.75	$155.70
Purchase #4	$79.93	13.727%	$90.902	$90.90	$90.90	$90.90
Purchase #5	$192.78	11.297%	$214.5584	$214.56	$214.55	$214.60
Purchase #6	$204.66	6.474%	$217.9097	$217.91	$217.90	$217.90
Purchase #7	$91.83	13.827%	$104.5273	$104.53	$104.55	$104.50
7 purchase totals =	$1,061.94		$1,174.0951	$1,174.10	$1,174.10	$1,174.10