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	$85.67	9.644%	$93.932	$93.93	$93.95	$93.90
Purchase #2	$203.46	9.362%	$222.5079	$222.51	$222.50	$222.50
Purchase #3	$29.93	6.547%	$31.8895	$31.89	$31.90	$31.90
Purchase #4	$244.54	10.535%	$270.3023	$270.30	$270.30	$270.30
Purchase #5	$214.67	3.846%	$222.9262	$222.93	$222.95	$222.90
Purchase #6	$29.39	8.618%	$31.9228	$31.92	$31.90	$31.90
Purchase #7	$134.98	4.705%	$141.3308	$141.33	$141.35	$141.30
7 purchase totals =	$942.64		$1,014.8115	$1,014.81	$1,014.85	$1,014.70