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	$189.40	5.547%	$199.906	$199.91	$199.90	$199.90
Purchase #2	$70.62	10.539%	$78.0626	$78.06	$78.05	$78.10
Purchase #3	$125.45	11.194%	$139.4929	$139.49	$139.50	$139.50
Purchase #4	$244.71	6.406%	$260.3861	$260.39	$260.40	$260.40
Purchase #5	$96.53	10.496%	$106.6618	$106.66	$106.65	$106.70
Purchase #6	$90.39	6.372%	$96.1497	$96.15	$96.15	$96.10
Purchase #7	$199.33	12.861%	$224.9658	$224.97	$224.95	$225.00
7 purchase totals =	$1,016.43		$1,105.6249	$1,105.63	$1,105.60	$1,105.70