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	$44.80	8.405%	$48.5654	$48.57	$48.55	$48.60
Purchase #2	$89.55	11.560%	$99.902	$99.90	$99.90	$99.90
Purchase #3	$90.60	9.465%	$99.1753	$99.18	$99.20	$99.20
Purchase #4	$109.90	9.192%	$120.002	$120.00	$120.00	$120.00
Purchase #5	$45.90	3.179%	$47.3592	$47.36	$47.35	$47.40
Purchase #6	$22.84	4.381%	$23.8406	$23.84	$23.85	$23.80
Purchase #7	$101.25	8.333%	$109.6872	$109.69	$109.70	$109.70
7 purchase totals =	$504.84		$548.5317	$548.54	$548.55	$548.60