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	$70.61	3.325%	$72.9578	$72.96	$72.95	$73.00
Purchase #2	$66.83	12.409%	$75.1229	$75.12	$75.10	$75.10
Purchase #3	$34.74	3.716%	$36.0309	$36.03	$36.05	$36.00
Purchase #4	$247.47	13.207%	$280.1534	$280.15	$280.15	$280.20
Purchase #5	$78.99	13.103%	$89.3401	$89.34	$89.35	$89.30
Purchase #6	$25.85	13.610%	$29.3682	$29.37	$29.35	$29.40
Purchase #7	$42.34	9.789%	$46.4847	$46.48	$46.50	$46.50
7 purchase totals =	$566.83		$629.4580	$629.45	$629.45	$629.50