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	$100.58	11.599%	$112.2463	$112.25	$112.25	$112.20
Purchase #2	$16.47	13.441%	$18.6837	$18.68	$18.70	$18.70
Purchase #3	$68.93	13.700%	$78.3734	$78.37	$78.35	$78.40
Purchase #4	$174.78	5.566%	$184.5083	$184.51	$184.50	$184.50
Purchase #5	$169.73	5.281%	$178.6934	$178.69	$178.70	$178.70
Purchase #6	$186.50	5.144%	$196.0936	$196.09	$196.10	$196.10
Purchase #7	$18.99	8.206%	$20.5483	$20.55	$20.55	$20.50
7 purchase totals =	$735.98		$789.1470	$789.14	$789.15	$789.10