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	$76.30	12.328%	$85.7063	$85.71	$85.70	$85.70
Purchase #2	$51.80	4.464%	$54.1124	$54.11	$54.10	$54.10
Purchase #3	$118.50	3.380%	$122.5053	$122.51	$122.50	$122.50
Purchase #4	$126.33	8.788%	$137.4319	$137.43	$137.45	$137.40
Purchase #5	$180.88	4.508%	$189.0341	$189.03	$189.05	$189.00
Purchase #6	$221.29	5.214%	$232.8281	$232.83	$232.85	$232.80
Purchase #7	$245.62	11.511%	$273.8933	$273.89	$273.90	$273.90
7 purchase totals =	$1,020.72		$1,095.5114	$1,095.51	$1,095.55	$1,095.40