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	$139.64	7.789%	$150.5166	$150.52	$150.50	$150.50
Purchase #2	$82.77	10.159%	$91.1786	$91.18	$91.20	$91.20
Purchase #3	$202.83	3.394%	$209.7141	$209.71	$209.70	$209.70
Purchase #4	$110.90	4.726%	$116.1411	$116.14	$116.15	$116.10
Purchase #5	$150.64	7.188%	$161.468	$161.47	$161.45	$161.50
Purchase #6	$197.57	5.537%	$208.5095	$208.51	$208.50	$208.50
Purchase #7	$240.47	9.520%	$263.3627	$263.36	$263.35	$263.40
7 purchase totals =	$1,124.82		$1,200.8906	$1,200.89	$1,200.85	$1,200.90