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	$152.77	9.247%	$166.8966	$166.90	$166.90	$166.90
Purchase #2	$242.80	3.764%	$251.939	$251.94	$251.95	$251.90
Purchase #3	$155.78	9.564%	$170.6788	$170.68	$170.70	$170.70
Purchase #4	$82.57	10.811%	$91.4966	$91.50	$91.50	$91.50
Purchase #5	$123.50	6.531%	$131.5658	$131.57	$131.55	$131.60
Purchase #6	$34.62	7.869%	$37.3442	$37.34	$37.35	$37.30
Purchase #7	$150.31	4.752%	$157.4527	$157.45	$157.45	$157.50
7 purchase totals =	$942.35		$1,007.3737	$1,007.38	$1,007.40	$1,007.40