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	$102.57	6.425%	$109.1601	$109.16	$109.15	$109.20
Purchase #2	$49.83	10.571%	$55.0975	$55.10	$55.10	$55.10
Purchase #3	$58.52	4.357%	$61.0697	$61.07	$61.05	$61.10
Purchase #4	$237.82	6.729%	$253.8229	$253.82	$253.80	$253.80
Purchase #5	$174.48	11.646%	$194.7999	$194.80	$194.80	$194.80
Purchase #6	$126.59	10.262%	$139.5807	$139.58	$139.60	$139.60
Purchase #7	$222.25	12.274%	$249.529	$249.53	$249.55	$249.50
7 purchase totals =	$972.06		$1,063.0598	$1,063.06	$1,063.05	$1,063.10