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	$172.84	7.357%	$185.5558	$185.56	$185.55	$185.60
Purchase #2	$160.31	6.668%	$170.9995	$171.00	$171.00	$171.00
Purchase #3	$233.59	9.193%	$255.0639	$255.06	$255.05	$255.10
Purchase #4	$67.94	12.540%	$76.4597	$76.46	$76.45	$76.50
Purchase #5	$109.40	13.130%	$123.7642	$123.76	$123.75	$123.80
Purchase #6	$199.76	4.769%	$209.2866	$209.29	$209.30	$209.30
Purchase #7	$164.57	7.326%	$176.6264	$176.63	$176.65	$176.60
7 purchase totals =	$1,108.41		$1,197.7561	$1,197.76	$1,197.75	$1,197.90