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	$165.66	13.764%	$188.4614	$188.46	$188.45	$188.50
Purchase #2	$169.91	9.165%	$185.4823	$185.48	$185.50	$185.50
Purchase #3	$118.43	6.572%	$126.2132	$126.21	$126.20	$126.20
Purchase #4	$173.96	9.734%	$190.8933	$190.89	$190.90	$190.90
Purchase #5	$49.66	10.368%	$54.8087	$54.81	$54.80	$54.80
Purchase #6	$231.35	10.443%	$255.5099	$255.51	$255.50	$255.50
Purchase #7	$151.75	3.819%	$157.5453	$157.55	$157.55	$157.50
7 purchase totals =	$1,060.72		$1,158.9141	$1,158.91	$1,158.90	$1,158.90