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	$154.90	8.842%	$168.5963	$168.60	$168.60	$168.60
Purchase #2	$234.72	11.302%	$261.2481	$261.25	$261.25	$261.20
Purchase #3	$79.98	4.313%	$83.4295	$83.43	$83.45	$83.40
Purchase #4	$23.63	4.756%	$24.7538	$24.75	$24.75	$24.80
Purchase #5	$177.55	6.746%	$189.5275	$189.53	$189.55	$189.50
Purchase #6	$65.80	9.672%	$72.1642	$72.16	$72.15	$72.20
Purchase #7	$237.40	7.738%	$255.77	$255.77	$255.75	$255.80
7 purchase totals =	$973.98		$1,055.4894	$1,055.49	$1,055.50	$1,055.50