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	$96.40	8.804%	$104.8871	$104.89	$104.90	$104.90
Purchase #2	$37.39	6.439%	$39.7975	$39.80	$39.80	$39.80
Purchase #3	$222.82	4.173%	$232.1183	$232.12	$232.10	$232.10
Purchase #4	$44.63	12.778%	$50.3328	$50.33	$50.35	$50.30
Purchase #5	$177.71	7.573%	$191.168	$191.17	$191.15	$191.20
Purchase #6	$213.52	4.871%	$223.9206	$223.92	$223.90	$223.90
Purchase #7	$123.31	7.570%	$132.6446	$132.64	$132.65	$132.60
7 purchase totals =	$915.78		$974.8689	$974.87	$974.85	$974.80