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	$27.84	9.230%	$30.4096	$30.41	$30.40	$30.40
Purchase #2	$167.26	3.443%	$173.0188	$173.02	$173.00	$173.00
Purchase #3	$30.88	11.871%	$34.5458	$34.55	$34.55	$34.50
Purchase #4	$36.65	10.746%	$40.5884	$40.59	$40.60	$40.60
Purchase #5	$167.41	7.455%	$179.8904	$179.89	$179.90	$179.90
Purchase #6	$89.28	11.689%	$99.7159	$99.72	$99.70	$99.70
Purchase #7	$206.62	10.454%	$228.2201	$228.22	$228.20	$228.20
7 purchase totals =	$725.94		$786.3890	$786.40	$786.35	$786.30