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	$124.47	5.609%	$131.4515	$131.45	$131.45	$131.50
Purchase #2	$233.51	13.738%	$265.5896	$265.59	$265.60	$265.60
Purchase #3	$40.83	10.808%	$45.2429	$45.24	$45.25	$45.20
Purchase #4	$140.83	4.364%	$146.9758	$146.98	$147.00	$147.00
Purchase #5	$214.90	9.520%	$235.3585	$235.36	$235.35	$235.40
Purchase #6	$69.87	3.738%	$72.4817	$72.48	$72.50	$72.50
Purchase #7	$186.89	9.639%	$204.9043	$204.90	$204.90	$204.90
7 purchase totals =	$1,011.30		$1,102.0043	$1,102.00	$1,102.05	$1,102.10