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	$215.93	13.530%	$245.1453	$245.15	$245.15	$245.10
Purchase #2	$164.50	12.500%	$185.0625	$185.06	$185.05	$185.10
Purchase #3	$135.72	11.185%	$150.9003	$150.90	$150.90	$150.90
Purchase #4	$186.85	5.139%	$196.4522	$196.45	$196.45	$196.50
Purchase #5	$16.92	10.277%	$18.6589	$18.66	$18.65	$18.70
Purchase #6	$56.73	9.873%	$62.331	$62.33	$62.35	$62.30
Purchase #7	$87.36	13.777%	$99.3956	$99.40	$99.40	$99.40
7 purchase totals =	$864.01		$957.9458	$957.95	$957.95	$958.00