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	$182.81	4.511%	$191.0566	$191.06	$191.05	$191.10
Purchase #2	$157.83	11.208%	$175.5196	$175.52	$175.50	$175.50
Purchase #3	$103.30	13.258%	$116.9955	$117.00	$117.00	$117.00
Purchase #4	$130.79	8.501%	$141.9085	$141.91	$141.90	$141.90
Purchase #5	$187.44	9.311%	$204.8925	$204.89	$204.90	$204.90
Purchase #6	$131.89	6.831%	$140.8994	$140.90	$140.90	$140.90
Purchase #7	$48.53	7.407%	$52.1246	$52.12	$52.10	$52.10
7 purchase totals =	$942.59		$1,023.3967	$1,023.40	$1,023.35	$1,023.40