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	$110.96	5.306%	$116.8475	$116.85	$116.85	$116.80
Purchase #2	$103.60	5.629%	$109.4316	$109.43	$109.45	$109.40
Purchase #3	$100.25	8.685%	$108.9567	$108.96	$108.95	$109.00
Purchase #4	$84.85	6.146%	$90.0649	$90.06	$90.05	$90.10
Purchase #5	$53.38	7.826%	$57.5575	$57.56	$57.55	$57.60
Purchase #6	$234.53	6.115%	$248.8715	$248.87	$248.85	$248.90
Purchase #7	$12.29	12.303%	$13.802	$13.80	$13.80	$13.80
7 purchase totals =	$699.86		$745.5317	$745.53	$745.50	$745.60