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	$83.69	3.103%	$86.2869	$86.29	$86.30	$86.30
Purchase #2	$87.66	3.218%	$90.4809	$90.48	$90.50	$90.50
Purchase #3	$37.88	3.633%	$39.2562	$39.26	$39.25	$39.30
Purchase #4	$40.76	6.648%	$43.4697	$43.47	$43.45	$43.50
Purchase #5	$243.57	6.848%	$260.2497	$260.25	$260.25	$260.20
Purchase #6	$72.89	12.817%	$82.2323	$82.23	$82.25	$82.20
Purchase #7	$215.90	4.330%	$225.2485	$225.25	$225.25	$225.20
7 purchase totals =	$782.35		$827.2242	$827.23	$827.25	$827.20