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	$90.25	11.189%	$100.3481	$100.35	$100.35	$100.30
Purchase #2	$92.72	13.658%	$105.3837	$105.38	$105.40	$105.40
Purchase #3	$14.67	7.451%	$15.7631	$15.76	$15.75	$15.80
Purchase #4	$170.65	12.428%	$191.8584	$191.86	$191.85	$191.90
Purchase #5	$233.85	12.830%	$263.853	$263.85	$263.85	$263.90
Purchase #6	$185.84	4.367%	$193.9556	$193.96	$193.95	$194.00
Purchase #7	$60.29	5.756%	$63.7603	$63.76	$63.75	$63.80
7 purchase totals =	$848.27		$934.9222	$934.92	$934.90	$935.10