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	$194.34	12.696%	$219.0134	$219.01	$219.00	$219.00
Purchase #2	$59.68	7.406%	$64.0999	$64.10	$64.10	$64.10
Purchase #3	$54.32	8.697%	$59.0442	$59.04	$59.05	$59.00
Purchase #4	$250.56	6.316%	$266.3854	$266.39	$266.40	$266.40
Purchase #5	$126.81	8.344%	$137.391	$137.39	$137.40	$137.40
Purchase #6	$185.57	5.820%	$196.3702	$196.37	$196.35	$196.40
Purchase #7	$135.45	6.444%	$144.1784	$144.18	$144.20	$144.20
7 purchase totals =	$1,006.73		$1,086.4825	$1,086.48	$1,086.50	$1,086.50