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	$195.89	6.582%	$208.7835	$208.78	$208.80	$208.80
Purchase #2	$168.33	6.662%	$179.5441	$179.54	$179.55	$179.50
Purchase #3	$154.94	5.648%	$163.691	$163.69	$163.70	$163.70
Purchase #4	$44.72	9.686%	$49.0516	$49.05	$49.05	$49.10
Purchase #5	$197.81	7.633%	$212.9088	$212.91	$212.90	$212.90
Purchase #6	$76.30	13.369%	$86.5005	$86.50	$86.50	$86.50
Purchase #7	$178.35	12.345%	$200.3673	$200.37	$200.35	$200.40
7 purchase totals =	$1,016.34		$1,100.8468	$1,100.84	$1,100.85	$1,100.90