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	$122.59	7.225%	$131.4471	$131.45	$131.45	$131.40
Purchase #2	$53.89	9.758%	$59.1486	$59.15	$59.15	$59.10
Purchase #3	$123.57	5.187%	$129.9796	$129.98	$130.00	$130.00
Purchase #4	$140.45	12.168%	$157.54	$157.54	$157.55	$157.50
Purchase #5	$94.41	5.717%	$99.8074	$99.81	$99.80	$99.80
Purchase #6	$137.92	8.155%	$149.1674	$149.17	$149.15	$149.20
Purchase #7	$24.42	3.837%	$25.357	$25.36	$25.35	$25.40
7 purchase totals =	$697.25		$752.4471	$752.46	$752.45	$752.40