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	$95.52	7.161%	$102.3602	$102.36	$102.35	$102.40
Purchase #2	$113.82	12.168%	$127.6696	$127.67	$127.65	$127.70
Purchase #3	$138.45	11.340%	$154.1502	$154.15	$154.15	$154.20
Purchase #4	$223.57	3.667%	$231.7683	$231.77	$231.75	$231.80
Purchase #5	$135.34	8.499%	$146.8425	$146.84	$146.85	$146.80
Purchase #6	$37.97	13.393%	$43.0553	$43.06	$43.05	$43.10
Purchase #7	$220.50	11.169%	$245.1276	$245.13	$245.15	$245.10
7 purchase totals =	$965.17		$1,050.9737	$1,050.98	$1,050.95	$1,051.10