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	$234.86	12.197%	$263.5059	$263.51	$263.50	$263.50
Purchase #2	$54.95	8.441%	$59.5883	$59.59	$59.60	$59.60
Purchase #3	$77.66	13.368%	$88.0416	$88.04	$88.05	$88.00
Purchase #4	$92.62	12.316%	$104.0271	$104.03	$104.05	$104.00
Purchase #5	$171.57	3.240%	$177.1289	$177.13	$177.15	$177.10
Purchase #6	$78.71	13.132%	$89.0462	$89.05	$89.05	$89.00
Purchase #7	$139.66	11.465%	$155.672	$155.67	$155.65	$155.70
7 purchase totals =	$850.03		$937.0100	$937.02	$937.05	$936.90