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	$14.84	3.681%	$15.3863	$15.39	$15.40	$15.40
Purchase #2	$179.86	13.301%	$203.7832	$203.78	$203.80	$203.80
Purchase #3	$148.39	4.187%	$154.6031	$154.60	$154.60	$154.60
Purchase #4	$136.90	10.421%	$151.1663	$151.17	$151.15	$151.20
Purchase #5	$227.69	4.843%	$238.717	$238.72	$238.70	$238.70
Purchase #6	$222.78	12.279%	$250.1352	$250.14	$250.15	$250.10
Purchase #7	$131.98	12.567%	$148.5659	$148.57	$148.55	$148.60
7 purchase totals =	$1,062.44		$1,162.3570	$1,162.37	$1,162.35	$1,162.40