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	$128.93	9.764%	$141.5187	$141.52	$141.50	$141.50
Purchase #2	$61.63	7.104%	$66.0082	$66.01	$66.00	$66.00
Purchase #3	$83.62	10.391%	$92.309	$92.31	$92.30	$92.30
Purchase #4	$139.26	13.701%	$158.34	$158.34	$158.35	$158.30
Purchase #5	$123.56	7.229%	$132.4922	$132.49	$132.50	$132.50
Purchase #6	$103.93	5.727%	$109.8821	$109.88	$109.90	$109.90
Purchase #7	$110.96	4.125%	$115.5371	$115.54	$115.55	$115.50
7 purchase totals =	$751.89		$816.0873	$816.09	$816.10	$816.00