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	$117.95	11.154%	$131.1061	$131.11	$131.10	$131.10
Purchase #2	$186.80	7.533%	$200.8716	$200.87	$200.85	$200.90
Purchase #3	$85.70	12.667%	$96.5556	$96.56	$96.55	$96.60
Purchase #4	$241.52	11.563%	$269.447	$269.45	$269.45	$269.40
Purchase #5	$38.32	4.517%	$40.0509	$40.05	$40.05	$40.10
Purchase #6	$65.76	7.441%	$70.6532	$70.65	$70.65	$70.70
Purchase #7	$91.30	5.661%	$96.4685	$96.47	$96.45	$96.50
7 purchase totals =	$827.35		$905.1529	$905.16	$905.10	$905.30