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	$179.57	5.455%	$189.3655	$189.37	$189.35	$189.40
Purchase #2	$142.78	7.188%	$153.043	$153.04	$153.05	$153.00
Purchase #3	$139.30	9.675%	$152.7773	$152.78	$152.80	$152.80
Purchase #4	$131.32	4.424%	$137.1296	$137.13	$137.15	$137.10
Purchase #5	$249.51	4.164%	$259.8996	$259.90	$259.90	$259.90
Purchase #6	$84.83	12.519%	$95.4499	$95.45	$95.45	$95.40
Purchase #7	$71.49	3.125%	$73.7241	$73.72	$73.70	$73.70
7 purchase totals =	$998.80		$1,061.3890	$1,061.39	$1,061.40	$1,061.30