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	$60.51	3.271%	$62.4893	$62.49	$62.50	$62.50
Purchase #2	$50.27	4.759%	$52.6623	$52.66	$52.65	$52.70
Purchase #3	$140.91	8.161%	$152.4097	$152.41	$152.40	$152.40
Purchase #4	$76.75	10.766%	$85.0129	$85.01	$85.00	$85.00
Purchase #5	$86.51	11.870%	$96.7787	$96.78	$96.80	$96.80
Purchase #6	$78.34	10.403%	$86.4897	$86.49	$86.50	$86.50
Purchase #7	$102.39	12.690%	$115.3833	$115.38	$115.40	$115.40
7 purchase totals =	$595.68		$651.2259	$651.22	$651.25	$651.30