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	$67.47	9.273%	$73.7265	$73.73	$73.75	$73.70
Purchase #2	$76.73	12.130%	$86.0373	$86.04	$86.05	$86.00
Purchase #3	$74.63	4.582%	$78.0495	$78.05	$78.05	$78.00
Purchase #4	$240.92	5.467%	$254.0911	$254.09	$254.10	$254.10
Purchase #5	$138.63	12.452%	$155.8922	$155.89	$155.90	$155.90
Purchase #6	$93.73	12.255%	$105.2166	$105.22	$105.20	$105.20
Purchase #7	$94.96	4.842%	$99.558	$99.56	$99.55	$99.60
7 purchase totals =	$787.07		$852.5712	$852.58	$852.60	$852.50