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	$188.42	12.772%	$212.485	$212.49	$212.50	$212.50
Purchase #2	$134.51	13.172%	$152.2277	$152.23	$152.25	$152.20
Purchase #3	$197.82	5.851%	$209.3944	$209.39	$209.40	$209.40
Purchase #4	$183.29	12.692%	$206.5532	$206.55	$206.55	$206.60
Purchase #5	$15.32	10.518%	$16.9314	$16.93	$16.95	$16.90
Purchase #6	$83.85	3.247%	$86.5726	$86.57	$86.55	$86.60
Purchase #7	$203.45	6.523%	$216.721	$216.72	$216.70	$216.70
7 purchase totals =	$1,006.66		$1,100.8853	$1,100.88	$1,100.90	$1,100.90