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	$132.43	3.520%	$137.0915	$137.09	$137.10	$137.10
Purchase #2	$147.39	5.744%	$155.8561	$155.86	$155.85	$155.90
Purchase #3	$183.30	4.259%	$191.1067	$191.11	$191.10	$191.10
Purchase #4	$152.64	5.513%	$161.055	$161.06	$161.05	$161.10
Purchase #5	$32.79	3.483%	$33.9321	$33.93	$33.95	$33.90
Purchase #6	$180.51	5.103%	$189.7214	$189.72	$189.70	$189.70
Purchase #7	$194.27	9.465%	$212.6577	$212.66	$212.65	$212.70
7 purchase totals =	$1,023.33		$1,081.4205	$1,081.43	$1,081.40	$1,081.50