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	$156.27	7.154%	$167.4496	$167.45	$167.45	$167.40
Purchase #2	$45.50	7.330%	$48.8352	$48.84	$48.85	$48.80
Purchase #3	$197.95	5.254%	$208.3503	$208.35	$208.35	$208.40
Purchase #4	$151.37	12.638%	$170.5001	$170.50	$170.50	$170.50
Purchase #5	$59.82	8.685%	$65.0154	$65.02	$65.00	$65.00
Purchase #6	$30.77	10.165%	$33.8978	$33.90	$33.90	$33.90
Purchase #7	$48.39	6.370%	$51.4724	$51.47	$51.45	$51.50
7 purchase totals =	$690.07		$745.5208	$745.53	$745.50	$745.50