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	$156.26	9.573%	$171.2188	$171.22	$171.20	$171.20
Purchase #2	$91.29	8.366%	$98.9273	$98.93	$98.95	$98.90
Purchase #3	$63.90	7.684%	$68.8101	$68.81	$68.80	$68.80
Purchase #4	$160.78	11.582%	$179.4015	$179.40	$179.40	$179.40
Purchase #5	$180.89	8.455%	$196.1842	$196.18	$196.20	$196.20
Purchase #6	$222.86	5.196%	$234.4398	$234.44	$234.45	$234.40
Purchase #7	$116.47	6.144%	$123.6259	$123.63	$123.65	$123.60
7 purchase totals =	$992.45		$1,072.6076	$1,072.61	$1,072.65	$1,072.50