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	$189.64	5.250%	$199.5961	$199.60	$199.60	$199.60
Purchase #2	$140.35	5.504%	$148.0749	$148.07	$148.05	$148.10
Purchase #3	$51.72	10.547%	$57.1749	$57.17	$57.15	$57.20
Purchase #4	$145.89	8.528%	$158.3315	$158.33	$158.35	$158.30
Purchase #5	$100.56	10.203%	$110.8201	$110.82	$110.80	$110.80
Purchase #6	$133.92	10.241%	$147.6347	$147.63	$147.65	$147.60
Purchase #7	$174.75	5.249%	$183.9226	$183.92	$183.90	$183.90
7 purchase totals =	$936.83		$1,005.5548	$1,005.54	$1,005.50	$1,005.50