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	$42.96	3.648%	$44.5272	$44.53	$44.55	$44.50
Purchase #2	$26.50	4.245%	$27.6249	$27.62	$27.60	$27.60
Purchase #3	$151.78	6.780%	$162.0707	$162.07	$162.05	$162.10
Purchase #4	$205.71	8.564%	$223.327	$223.33	$223.35	$223.30
Purchase #5	$37.63	13.252%	$42.6167	$42.62	$42.60	$42.60
Purchase #6	$71.73	8.763%	$78.0157	$78.02	$78.00	$78.00
Purchase #7	$209.61	13.619%	$238.1568	$238.16	$238.15	$238.20
7 purchase totals =	$745.92		$816.3390	$816.35	$816.30	$816.30