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	$62.78	9.727%	$68.8866	$68.89	$68.90	$68.90
Purchase #2	$81.96	9.468%	$89.72	$89.72	$89.70	$89.70
Purchase #3	$191.41	11.726%	$213.8547	$213.85	$213.85	$213.90
Purchase #4	$206.69	5.557%	$218.1758	$218.18	$218.20	$218.20
Purchase #5	$172.77	7.295%	$185.3736	$185.37	$185.35	$185.40
Purchase #6	$40.88	13.831%	$46.5341	$46.53	$46.55	$46.50
Purchase #7	$249.80	13.683%	$283.9801	$283.98	$284.00	$284.00
7 purchase totals =	$1,006.29		$1,106.5249	$1,106.52	$1,106.55	$1,106.60