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	$166.81	3.154%	$172.0712	$172.07	$172.05	$172.10
Purchase #2	$166.26	3.314%	$171.7699	$171.77	$171.75	$171.80
Purchase #3	$164.58	9.806%	$180.7187	$180.72	$180.70	$180.70
Purchase #4	$20.63	11.741%	$23.0522	$23.05	$23.05	$23.10
Purchase #5	$239.57	9.738%	$262.8993	$262.90	$262.90	$262.90
Purchase #6	$43.78	6.208%	$46.4979	$46.50	$46.50	$46.50
Purchase #7	$151.27	9.263%	$165.2821	$165.28	$165.30	$165.30
7 purchase totals =	$952.90		$1,022.2913	$1,022.29	$1,022.25	$1,022.40