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	$205.61	8.616%	$223.3254	$223.33	$223.35	$223.30
Purchase #2	$73.76	12.387%	$82.8967	$82.90	$82.90	$82.90
Purchase #3	$33.41	7.292%	$35.8463	$35.85	$35.85	$35.80
Purchase #4	$151.97	5.421%	$160.2083	$160.21	$160.20	$160.20
Purchase #5	$187.31	11.360%	$208.5884	$208.59	$208.60	$208.60
Purchase #6	$33.36	3.297%	$34.4599	$34.46	$34.45	$34.50
Purchase #7	$130.44	5.493%	$137.6051	$137.61	$137.60	$137.60
7 purchase totals =	$815.86		$882.9301	$882.95	$882.95	$882.90