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	$91.51	6.420%	$97.3849	$97.38	$97.40	$97.40
Purchase #2	$55.79	6.218%	$59.259	$59.26	$59.25	$59.30
Purchase #3	$14.73	3.142%	$15.1928	$15.19	$15.20	$15.20
Purchase #4	$92.53	5.435%	$97.559	$97.56	$97.55	$97.60
Purchase #5	$157.33	8.437%	$170.6039	$170.60	$170.60	$170.60
Purchase #6	$81.60	10.840%	$90.4454	$90.45	$90.45	$90.40
Purchase #7	$165.41	13.830%	$188.2862	$188.29	$188.30	$188.30
7 purchase totals =	$658.90		$718.7312	$718.73	$718.75	$718.80