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	$57.37	3.465%	$59.3579	$59.36	$59.35	$59.40
Purchase #2	$234.53	3.152%	$241.9224	$241.92	$241.90	$241.90
Purchase #3	$209.78	6.330%	$223.0591	$223.06	$223.05	$223.10
Purchase #4	$208.62	3.626%	$216.1846	$216.18	$216.20	$216.20
Purchase #5	$151.99	12.835%	$171.4979	$171.50	$171.50	$171.50
Purchase #6	$217.67	3.516%	$225.3233	$225.32	$225.30	$225.30
Purchase #7	$203.47	9.859%	$223.5301	$223.53	$223.55	$223.50
7 purchase totals =	$1,283.43		$1,360.8753	$1,360.87	$1,360.85	$1,360.90