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	$117.75	11.754%	$131.5903	$131.59	$131.60	$131.60
Purchase #2	$56.27	9.272%	$61.4874	$61.49	$61.50	$61.50
Purchase #3	$100.60	11.497%	$112.166	$112.17	$112.15	$112.20
Purchase #4	$190.61	5.709%	$201.4919	$201.49	$201.50	$201.50
Purchase #5	$46.95	8.196%	$50.798	$50.80	$50.80	$50.80
Purchase #6	$229.76	7.105%	$246.0844	$246.08	$246.10	$246.10
Purchase #7	$116.57	9.643%	$127.8108	$127.81	$127.80	$127.80
7 purchase totals =	$858.51		$931.4288	$931.43	$931.45	$931.50