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	$40.63	5.821%	$42.9951	$43.00	$43.00	$43.00
Purchase #2	$237.39	4.277%	$247.5432	$247.54	$247.55	$247.50
Purchase #3	$190.90	4.837%	$200.1338	$200.13	$200.15	$200.10
Purchase #4	$190.45	13.158%	$215.5094	$215.51	$215.50	$215.50
Purchase #5	$146.65	6.689%	$156.4594	$156.46	$156.45	$156.50
Purchase #6	$33.35	6.518%	$35.5238	$35.52	$35.50	$35.50
Purchase #7	$204.57	13.713%	$232.6227	$232.62	$232.60	$232.60
7 purchase totals =	$1,043.94		$1,130.7874	$1,130.78	$1,130.75	$1,130.70