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	$95.36	13.808%	$108.5273	$108.53	$108.55	$108.50
Purchase #2	$93.39	12.271%	$104.8499	$104.85	$104.85	$104.80
Purchase #3	$43.31	10.311%	$47.7757	$47.78	$47.80	$47.80
Purchase #4	$178.89	6.349%	$190.2477	$190.25	$190.25	$190.20
Purchase #5	$64.69	4.763%	$67.7712	$67.77	$67.75	$67.80
Purchase #6	$159.76	5.199%	$168.0659	$168.07	$168.05	$168.10
Purchase #7	$227.26	11.844%	$254.1767	$254.18	$254.20	$254.20
7 purchase totals =	$862.66		$941.4144	$941.43	$941.45	$941.40