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	$206.93	4.571%	$216.3888	$216.39	$216.40	$216.40
Purchase #2	$208.58	12.289%	$234.2124	$234.21	$234.20	$234.20
Purchase #3	$187.54	3.747%	$194.5671	$194.57	$194.55	$194.60
Purchase #4	$13.89	10.541%	$15.3541	$15.35	$15.35	$15.40
Purchase #5	$152.34	9.564%	$166.9098	$166.91	$166.90	$166.90
Purchase #6	$173.50	13.446%	$196.8288	$196.83	$196.85	$196.80
Purchase #7	$131.83	13.793%	$150.0133	$150.01	$150.00	$150.00
7 purchase totals =	$1,074.61		$1,174.2743	$1,174.27	$1,174.25	$1,174.30