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	$149.43	5.638%	$157.8549	$157.85	$157.85	$157.90
Purchase #2	$161.39	4.396%	$168.4847	$168.48	$168.50	$168.50
Purchase #3	$99.56	13.110%	$112.6123	$112.61	$112.60	$112.60
Purchase #4	$77.41	8.184%	$83.7452	$83.75	$83.75	$83.70
Purchase #5	$73.93	4.230%	$77.0572	$77.06	$77.05	$77.10
Purchase #6	$89.46	12.800%	$100.9109	$100.91	$100.90	$100.90
Purchase #7	$170.88	6.687%	$182.3067	$182.31	$182.30	$182.30
7 purchase totals =	$822.06		$882.9719	$882.97	$882.95	$883.00