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	$61.71	5.441%	$65.0676	$65.07	$65.05	$65.10
Purchase #2	$39.29	5.323%	$41.3814	$41.38	$41.40	$41.40
Purchase #3	$160.64	4.839%	$168.4134	$168.41	$168.40	$168.40
Purchase #4	$232.73	12.783%	$262.4799	$262.48	$262.50	$262.50
Purchase #5	$150.90	11.298%	$167.9487	$167.95	$167.95	$167.90
Purchase #6	$129.92	5.164%	$136.6291	$136.63	$136.65	$136.60
Purchase #7	$111.36	7.708%	$119.9436	$119.94	$119.95	$119.90
7 purchase totals =	$886.55		$961.8637	$961.86	$961.90	$961.80