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	$125.63	9.137%	$137.1088	$137.11	$137.10	$137.10
Purchase #2	$233.55	5.511%	$246.4209	$246.42	$246.40	$246.40
Purchase #3	$76.72	12.462%	$86.2808	$86.28	$86.30	$86.30
Purchase #4	$85.81	3.484%	$88.7996	$88.80	$88.80	$88.80
Purchase #5	$204.32	13.243%	$231.3781	$231.38	$231.40	$231.40
Purchase #6	$165.50	4.329%	$172.6645	$172.66	$172.65	$172.70
Purchase #7	$177.62	4.301%	$185.2594	$185.26	$185.25	$185.30
7 purchase totals =	$1,069.15		$1,147.9121	$1,147.91	$1,147.90	$1,148.00