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	$185.52	12.417%	$208.556	$208.56	$208.55	$208.60
Purchase #2	$82.71	9.102%	$90.2383	$90.24	$90.25	$90.20
Purchase #3	$91.72	9.235%	$100.1903	$100.19	$100.20	$100.20
Purchase #4	$182.58	13.687%	$207.5697	$207.57	$207.55	$207.60
Purchase #5	$230.76	4.341%	$240.7773	$240.78	$240.80	$240.80
Purchase #6	$234.70	6.684%	$250.3873	$250.39	$250.40	$250.40
Purchase #7	$83.55	5.484%	$88.1319	$88.13	$88.15	$88.10
7 purchase totals =	$1,091.54		$1,185.8508	$1,185.86	$1,185.90	$1,185.90