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	$197.76	12.491%	$222.4622	$222.46	$222.45	$222.50
Purchase #2	$209.58	6.145%	$222.4587	$222.46	$222.45	$222.50
Purchase #3	$29.37	12.612%	$33.0741	$33.07	$33.05	$33.10
Purchase #4	$223.94	7.648%	$241.0669	$241.07	$241.05	$241.10
Purchase #5	$105.38	8.240%	$114.0633	$114.06	$114.05	$114.10
Purchase #6	$91.93	3.655%	$95.29	$95.29	$95.30	$95.30
Purchase #7	$192.59	5.661%	$203.4925	$203.49	$203.50	$203.50
7 purchase totals =	$1,050.55		$1,131.9077	$1,131.90	$1,131.85	$1,132.10