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	$179.65	9.710%	$197.094	$197.09	$197.10	$197.10
Purchase #2	$234.89	13.339%	$266.222	$266.22	$266.20	$266.20
Purchase #3	$196.74	6.686%	$209.894	$209.89	$209.90	$209.90
Purchase #4	$243.80	5.360%	$256.8677	$256.87	$256.85	$256.90
Purchase #5	$88.29	13.116%	$99.8701	$99.87	$99.85	$99.90
Purchase #6	$109.27	4.240%	$113.903	$113.90	$113.90	$113.90
Purchase #7	$157.66	10.136%	$173.6404	$173.64	$173.65	$173.60
7 purchase totals =	$1,210.30		$1,317.4912	$1,317.48	$1,317.45	$1,317.50