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	$38.31	4.674%	$40.1006	$40.10	$40.10	$40.10
Purchase #2	$67.62	5.105%	$71.072	$71.07	$71.05	$71.10
Purchase #3	$138.43	7.480%	$148.7846	$148.78	$148.80	$148.80
Purchase #4	$73.46	6.658%	$78.351	$78.35	$78.35	$78.40
Purchase #5	$201.83	4.240%	$210.3876	$210.39	$210.40	$210.40
Purchase #6	$197.27	7.553%	$212.1698	$212.17	$212.15	$212.20
Purchase #7	$211.71	13.775%	$240.8731	$240.87	$240.85	$240.90
7 purchase totals =	$928.63		$1,001.7387	$1,001.73	$1,001.70	$1,001.90