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	$97.33	12.791%	$109.7795	$109.78	$109.80	$109.80
Purchase #2	$97.56	12.319%	$109.5784	$109.58	$109.60	$109.60
Purchase #3	$112.93	5.706%	$119.3738	$119.37	$119.35	$119.40
Purchase #4	$141.72	4.529%	$148.1385	$148.14	$148.15	$148.10
Purchase #5	$89.68	5.330%	$94.4599	$94.46	$94.45	$94.50
Purchase #6	$160.77	11.382%	$179.0688	$179.07	$179.05	$179.10
Purchase #7	$123.88	10.533%	$136.9283	$136.93	$136.95	$136.90
7 purchase totals =	$823.87		$897.3272	$897.33	$897.35	$897.40