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	$10.26	10.382%	$11.3252	$11.33	$11.35	$11.30
Purchase #2	$29.80	9.576%	$32.6536	$32.65	$32.65	$32.70
Purchase #3	$79.86	12.858%	$90.1284	$90.13	$90.15	$90.10
Purchase #4	$176.40	11.474%	$196.6401	$196.64	$196.65	$196.60
Purchase #5	$111.94	7.318%	$120.1318	$120.13	$120.15	$120.10
Purchase #6	$161.50	8.370%	$175.0176	$175.02	$175.00	$175.00
Purchase #7	$197.67	5.614%	$208.7672	$208.77	$208.75	$208.80
7 purchase totals =	$767.43		$834.6639	$834.67	$834.70	$834.60