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	$159.50	7.793%	$171.9298	$171.93	$171.95	$171.90
Purchase #2	$101.76	7.331%	$109.22	$109.22	$109.20	$109.20
Purchase #3	$212.29	10.450%	$234.4743	$234.47	$234.45	$234.50
Purchase #4	$108.78	13.678%	$123.6589	$123.66	$123.65	$123.70
Purchase #5	$204.51	7.271%	$219.3799	$219.38	$219.40	$219.40
Purchase #6	$129.35	11.239%	$143.8876	$143.89	$143.90	$143.90
Purchase #7	$98.85	13.871%	$112.5615	$112.56	$112.55	$112.60
7 purchase totals =	$1,015.04		$1,115.1120	$1,115.11	$1,115.10	$1,115.20