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	$203.87	4.699%	$213.4499	$213.45	$213.45	$213.40
Purchase #2	$75.93	12.406%	$85.3499	$85.35	$85.35	$85.30
Purchase #3	$198.42	6.784%	$211.8808	$211.88	$211.90	$211.90
Purchase #4	$174.51	12.846%	$196.9276	$196.93	$196.95	$196.90
Purchase #5	$140.44	12.421%	$157.8841	$157.88	$157.90	$157.90
Purchase #6	$21.44	3.861%	$22.2678	$22.27	$22.25	$22.30
Purchase #7	$50.84	7.104%	$54.4517	$54.45	$54.45	$54.50
7 purchase totals =	$865.45		$942.2118	$942.21	$942.25	$942.20