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	$159.64	4.619%	$167.0138	$167.01	$167.00	$167.00
Purchase #2	$239.37	8.177%	$258.9433	$258.94	$258.95	$258.90
Purchase #3	$196.31	13.745%	$223.2928	$223.29	$223.30	$223.30
Purchase #4	$187.87	6.429%	$199.9482	$199.95	$199.95	$199.90
Purchase #5	$29.48	6.567%	$31.416	$31.42	$31.40	$31.40
Purchase #6	$60.97	11.395%	$67.9175	$67.92	$67.90	$67.90
Purchase #7	$69.64	3.191%	$71.8622	$71.86	$71.85	$71.90
7 purchase totals =	$943.28		$1,020.3938	$1,020.39	$1,020.35	$1,020.30