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	$166.76	7.831%	$179.819	$179.82	$179.80	$179.80
Purchase #2	$148.74	12.237%	$166.9413	$166.94	$166.95	$166.90
Purchase #3	$175.78	7.616%	$189.1674	$189.17	$189.15	$189.20
Purchase #4	$210.46	9.787%	$231.0577	$231.06	$231.05	$231.10
Purchase #5	$47.88	12.130%	$53.6878	$53.69	$53.70	$53.70
Purchase #6	$54.43	9.317%	$59.5012	$59.50	$59.50	$59.50
Purchase #7	$58.97	8.344%	$63.8905	$63.89	$63.90	$63.90
7 purchase totals =	$863.02		$944.0649	$944.07	$944.05	$944.10