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	$81.41	5.333%	$85.7516	$85.75	$85.75	$85.80
Purchase #2	$203.87	8.196%	$220.5792	$220.58	$220.60	$220.60
Purchase #3	$243.90	12.717%	$274.9168	$274.92	$274.90	$274.90
Purchase #4	$59.44	12.486%	$66.8617	$66.86	$66.85	$66.90
Purchase #5	$31.34	4.747%	$32.8277	$32.83	$32.85	$32.80
Purchase #6	$212.48	11.796%	$237.5441	$237.54	$237.55	$237.50
Purchase #7	$77.27	11.854%	$86.4296	$86.43	$86.45	$86.40
7 purchase totals =	$909.71		$1,004.9107	$1,004.91	$1,004.95	$1,004.90