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	$148.59	11.257%	$165.3168	$165.32	$165.30	$165.30
Purchase #2	$43.88	6.196%	$46.5988	$46.60	$46.60	$46.60
Purchase #3	$147.35	12.782%	$166.1843	$166.18	$166.20	$166.20
Purchase #4	$149.42	8.257%	$161.7576	$161.76	$161.75	$161.80
Purchase #5	$231.39	5.820%	$244.8569	$244.86	$244.85	$244.90
Purchase #6	$73.70	3.438%	$76.2338	$76.23	$76.25	$76.20
Purchase #7	$209.71	5.330%	$220.8875	$220.89	$220.90	$220.90
7 purchase totals =	$1,004.04		$1,081.8357	$1,081.84	$1,081.85	$1,081.90