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	$159.63	4.533%	$166.866	$166.87	$166.85	$166.90
Purchase #2	$161.86	11.518%	$180.503	$180.50	$180.50	$180.50
Purchase #3	$71.93	11.673%	$80.3264	$80.33	$80.35	$80.30
Purchase #4	$141.34	12.863%	$159.5206	$159.52	$159.50	$159.50
Purchase #5	$157.89	8.778%	$171.7496	$171.75	$171.75	$171.70
Purchase #6	$18.90	7.748%	$20.3644	$20.36	$20.35	$20.40
Purchase #7	$236.91	3.126%	$244.3158	$244.32	$244.30	$244.30
7 purchase totals =	$948.46		$1,023.6458	$1,023.65	$1,023.60	$1,023.60