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	$20.85	5.167%	$21.9273	$21.93	$21.95	$21.90
Purchase #2	$207.39	3.462%	$214.5698	$214.57	$214.55	$214.60
Purchase #3	$168.54	4.369%	$175.9035	$175.90	$175.90	$175.90
Purchase #4	$151.86	13.353%	$172.1379	$172.14	$172.15	$172.10
Purchase #5	$176.78	13.515%	$200.6718	$200.67	$200.65	$200.70
Purchase #6	$140.25	7.197%	$150.3438	$150.34	$150.35	$150.30
Purchase #7	$225.70	13.398%	$255.9393	$255.94	$255.95	$255.90
7 purchase totals =	$1,091.37		$1,191.4934	$1,191.49	$1,191.50	$1,191.40