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	$129.25	8.515%	$140.2556	$140.26	$140.25	$140.30
Purchase #2	$87.37	4.769%	$91.5367	$91.54	$91.55	$91.50
Purchase #3	$198.77	13.340%	$225.2859	$225.29	$225.30	$225.30
Purchase #4	$92.50	11.597%	$103.2272	$103.23	$103.25	$103.20
Purchase #5	$152.37	8.246%	$164.9344	$164.93	$164.95	$164.90
Purchase #6	$152.83	6.350%	$162.5347	$162.53	$162.55	$162.50
Purchase #7	$237.76	4.415%	$248.2571	$248.26	$248.25	$248.30
7 purchase totals =	$1,050.85		$1,136.0316	$1,136.04	$1,136.10	$1,136.00