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	$212.37	7.226%	$227.7159	$227.72	$227.70	$227.70
Purchase #2	$215.42	4.282%	$224.6443	$224.64	$224.65	$224.60
Purchase #3	$175.32	13.703%	$199.3441	$199.34	$199.35	$199.30
Purchase #4	$146.67	13.270%	$166.1331	$166.13	$166.15	$166.10
Purchase #5	$84.59	13.664%	$96.1484	$96.15	$96.15	$96.10
Purchase #6	$82.65	10.193%	$91.0745	$91.07	$91.05	$91.10
Purchase #7	$38.32	10.608%	$42.385	$42.39	$42.40	$42.40
7 purchase totals =	$955.34		$1,047.4453	$1,047.44	$1,047.45	$1,047.30