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	$87.43	3.846%	$90.7926	$90.79	$90.80	$90.80
Purchase #2	$55.51	11.438%	$61.8592	$61.86	$61.85	$61.90
Purchase #3	$102.42	4.380%	$106.906	$106.91	$106.90	$106.90
Purchase #4	$55.51	7.396%	$59.6155	$59.62	$59.60	$59.60
Purchase #5	$113.50	4.334%	$118.4191	$118.42	$118.40	$118.40
Purchase #6	$230.61	10.378%	$254.5427	$254.54	$254.55	$254.50
Purchase #7	$6.38	13.480%	$7.24	$7.24	$7.25	$7.20
7 purchase totals =	$651.36		$699.3751	$699.38	$699.35	$699.30