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	$181.50	5.331%	$191.1758	$191.18	$191.20	$191.20
Purchase #2	$31.89	7.596%	$34.3124	$34.31	$34.30	$34.30
Purchase #3	$213.39	9.830%	$234.3662	$234.37	$234.35	$234.40
Purchase #4	$17.59	13.149%	$19.9029	$19.90	$19.90	$19.90
Purchase #5	$47.83	6.539%	$50.9576	$50.96	$50.95	$51.00
Purchase #6	$214.39	13.546%	$243.4313	$243.43	$243.45	$243.40
Purchase #7	$82.35	3.794%	$85.4744	$85.47	$85.45	$85.50
7 purchase totals =	$788.94		$859.6206	$859.62	$859.60	$859.70