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	$117.26	8.756%	$127.5273	$127.53	$127.55	$127.50
Purchase #2	$120.31	6.344%	$127.9425	$127.94	$127.95	$127.90
Purchase #3	$37.98	7.667%	$40.8919	$40.89	$40.90	$40.90
Purchase #4	$150.82	6.770%	$161.0305	$161.03	$161.05	$161.00
Purchase #5	$110.53	8.231%	$119.6277	$119.63	$119.65	$119.60
Purchase #6	$172.59	4.615%	$180.555	$180.56	$180.55	$180.60
Purchase #7	$61.66	12.216%	$69.1924	$69.19	$69.20	$69.20
7 purchase totals =	$771.15		$826.7673	$826.77	$826.85	$826.70