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	$19.42	4.700%	$20.3327	$20.33	$20.35	$20.30
Purchase #2	$62.35	13.330%	$70.6613	$70.66	$70.65	$70.70
Purchase #3	$132.51	11.255%	$147.424	$147.42	$147.40	$147.40
Purchase #4	$84.81	5.667%	$89.6162	$89.62	$89.60	$89.60
Purchase #5	$224.81	13.577%	$255.3325	$255.33	$255.35	$255.30
Purchase #6	$5.64	5.359%	$5.9422	$5.94	$5.95	$5.90
Purchase #7	$139.72	4.587%	$146.129	$146.13	$146.15	$146.10
7 purchase totals =	$669.26		$735.4379	$735.43	$735.45	$735.30