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	$233.34	10.731%	$258.3797	$258.38	$258.40	$258.40
Purchase #2	$129.64	12.314%	$145.6039	$145.60	$145.60	$145.60
Purchase #3	$49.47	5.786%	$52.3323	$52.33	$52.35	$52.30
Purchase #4	$219.50	3.145%	$226.4033	$226.40	$226.40	$226.40
Purchase #5	$44.38	13.369%	$50.3132	$50.31	$50.30	$50.30
Purchase #6	$95.77	12.859%	$108.0851	$108.09	$108.10	$108.10
Purchase #7	$201.56	10.222%	$222.1635	$222.16	$222.15	$222.20
7 purchase totals =	$973.66		$1,063.2810	$1,063.27	$1,063.30	$1,063.30