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	$76.79	6.160%	$81.5203	$81.52	$81.50	$81.50
Purchase #2	$89.34	7.389%	$95.9413	$95.94	$95.95	$95.90
Purchase #3	$110.38	4.797%	$115.6749	$115.67	$115.65	$115.70
Purchase #4	$186.83	13.158%	$211.4131	$211.41	$211.40	$211.40
Purchase #5	$74.48	8.602%	$80.8868	$80.89	$80.90	$80.90
Purchase #6	$119.75	6.869%	$127.9756	$127.98	$128.00	$128.00
Purchase #7	$104.82	6.797%	$111.9446	$111.94	$111.95	$111.90
7 purchase totals =	$762.39		$825.3566	$825.35	$825.35	$825.30