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	$33.63	12.612%	$37.8714	$37.87	$37.85	$37.90
Purchase #2	$79.53	3.175%	$82.0551	$82.06	$82.05	$82.10
Purchase #3	$133.60	3.164%	$137.8271	$137.83	$137.85	$137.80
Purchase #4	$83.88	12.330%	$94.2224	$94.22	$94.20	$94.20
Purchase #5	$232.79	3.731%	$241.4754	$241.48	$241.50	$241.50
Purchase #6	$223.47	8.856%	$243.2605	$243.26	$243.25	$243.30
Purchase #7	$133.84	3.548%	$138.5886	$138.59	$138.60	$138.60
7 purchase totals =	$920.74		$975.3005	$975.31	$975.30	$975.40