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	$45.73	13.325%	$51.8235	$51.82	$51.80	$51.80
Purchase #2	$7.46	4.135%	$7.7685	$7.77	$7.75	$7.80
Purchase #3	$184.69	8.473%	$200.3388	$200.34	$200.35	$200.30
Purchase #4	$59.82	12.491%	$67.2921	$67.29	$67.30	$67.30
Purchase #5	$98.36	12.505%	$110.6599	$110.66	$110.65	$110.70
Purchase #6	$66.56	9.111%	$72.6243	$72.62	$72.60	$72.60
Purchase #7	$239.54	5.803%	$253.4405	$253.44	$253.45	$253.40
7 purchase totals =	$702.16		$763.9476	$763.94	$763.90	$763.90