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	$54.88	7.487%	$58.9889	$58.99	$59.00	$59.00
Purchase #2	$156.55	9.371%	$171.2203	$171.22	$171.20	$171.20
Purchase #3	$85.78	10.725%	$94.9799	$94.98	$95.00	$95.00
Purchase #4	$90.34	10.388%	$99.7245	$99.72	$99.70	$99.70
Purchase #5	$197.77	9.265%	$216.0934	$216.09	$216.10	$216.10
Purchase #6	$146.48	6.583%	$156.1228	$156.12	$156.10	$156.10
Purchase #7	$226.49	6.623%	$241.4904	$241.49	$241.50	$241.50
7 purchase totals =	$958.29		$1,038.6202	$1,038.61	$1,038.60	$1,038.60