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	$76.78	11.309%	$85.4631	$85.46	$85.45	$85.50
Purchase #2	$208.52	6.148%	$221.3398	$221.34	$221.35	$221.30
Purchase #3	$233.30	7.337%	$250.4172	$250.42	$250.40	$250.40
Purchase #4	$109.93	3.633%	$113.9238	$113.92	$113.90	$113.90
Purchase #5	$39.46	6.495%	$42.0229	$42.02	$42.00	$42.00
Purchase #6	$171.35	4.762%	$179.5097	$179.51	$179.50	$179.50
Purchase #7	$131.83	7.573%	$141.8135	$141.81	$141.80	$141.80
7 purchase totals =	$971.17		$1,034.4900	$1,034.48	$1,034.40	$1,034.40