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	$8.29	6.552%	$8.8332	$8.83	$8.85	$8.80
Purchase #2	$168.87	9.574%	$185.0376	$185.04	$185.05	$185.00
Purchase #3	$81.52	6.377%	$86.7185	$86.72	$86.70	$86.70
Purchase #4	$29.50	10.417%	$32.573	$32.57	$32.55	$32.60
Purchase #5	$202.72	4.794%	$212.4384	$212.44	$212.45	$212.40
Purchase #6	$53.90	11.121%	$59.8942	$59.89	$59.90	$59.90
Purchase #7	$157.49	7.446%	$169.2167	$169.22	$169.20	$169.20
7 purchase totals =	$702.29		$754.7116	$754.71	$754.70	$754.60