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	$224.55	11.723%	$250.874	$250.87	$250.85	$250.90
Purchase #2	$56.96	4.128%	$59.3113	$59.31	$59.30	$59.30
Purchase #3	$126.98	4.579%	$132.7944	$132.79	$132.80	$132.80
Purchase #4	$93.36	11.436%	$104.0366	$104.04	$104.05	$104.00
Purchase #5	$231.97	10.234%	$255.7098	$255.71	$255.70	$255.70
Purchase #6	$247.64	11.134%	$275.2122	$275.21	$275.20	$275.20
Purchase #7	$188.90	6.321%	$200.8404	$200.84	$200.85	$200.80
7 purchase totals =	$1,170.36		$1,278.7787	$1,278.77	$1,278.75	$1,278.70