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	$83.94	10.567%	$92.8099	$92.81	$92.80	$92.80
Purchase #2	$109.74	13.365%	$124.4068	$124.41	$124.40	$124.40
Purchase #3	$151.72	11.277%	$168.8295	$168.83	$168.85	$168.80
Purchase #4	$179.75	7.803%	$193.7759	$193.78	$193.80	$193.80
Purchase #5	$112.80	9.170%	$123.1438	$123.14	$123.15	$123.10
Purchase #6	$130.83	9.806%	$143.6592	$143.66	$143.65	$143.70
Purchase #7	$137.79	10.607%	$152.4054	$152.41	$152.40	$152.40
7 purchase totals =	$906.57		$999.0305	$999.04	$999.05	$999.00