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	$105.59	3.247%	$109.0185	$109.02	$109.00	$109.00
Purchase #2	$152.61	6.514%	$162.551	$162.55	$162.55	$162.60
Purchase #3	$69.74	4.488%	$72.8699	$72.87	$72.85	$72.90
Purchase #4	$30.74	9.746%	$33.7359	$33.74	$33.75	$33.70
Purchase #5	$123.42	4.471%	$128.9381	$128.94	$128.95	$128.90
Purchase #6	$22.70	12.578%	$25.5552	$25.56	$25.55	$25.60
Purchase #7	$13.83	9.767%	$15.1808	$15.18	$15.20	$15.20
7 purchase totals =	$518.63		$547.8494	$547.86	$547.85	$547.90