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	$45.98	7.313%	$49.3425	$49.34	$49.35	$49.30
Purchase #2	$49.39	12.662%	$55.6438	$55.64	$55.65	$55.60
Purchase #3	$141.33	6.791%	$150.9277	$150.93	$150.95	$150.90
Purchase #4	$155.77	7.539%	$167.5135	$167.51	$167.50	$167.50
Purchase #5	$168.32	6.864%	$179.8735	$179.87	$179.85	$179.90
Purchase #6	$217.44	12.651%	$244.9483	$244.95	$244.95	$244.90
Purchase #7	$183.79	3.768%	$190.7152	$190.72	$190.70	$190.70
7 purchase totals =	$962.02		$1,038.9645	$1,038.96	$1,038.95	$1,038.80