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	$204.50	12.339%	$229.7333	$229.73	$229.75	$229.70
Purchase #2	$89.60	12.146%	$100.4828	$100.48	$100.50	$100.50
Purchase #3	$168.40	8.465%	$182.6551	$182.66	$182.65	$182.70
Purchase #4	$234.54	8.638%	$254.7996	$254.80	$254.80	$254.80
Purchase #5	$231.65	12.415%	$260.4093	$260.41	$260.40	$260.40
Purchase #6	$240.98	5.874%	$255.1352	$255.14	$255.15	$255.10
Purchase #7	$76.43	7.689%	$82.3067	$82.31	$82.30	$82.30
7 purchase totals =	$1,246.10		$1,365.5220	$1,365.53	$1,365.55	$1,365.50