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	$207.96	11.504%	$231.8837	$231.88	$231.90	$231.90
Purchase #2	$87.49	11.278%	$97.3571	$97.36	$97.35	$97.40
Purchase #3	$70.54	4.559%	$73.7559	$73.76	$73.75	$73.80
Purchase #4	$248.94	6.252%	$264.5037	$264.50	$264.50	$264.50
Purchase #5	$44.41	13.427%	$50.3729	$50.37	$50.35	$50.40
Purchase #6	$75.78	13.225%	$85.8019	$85.80	$85.80	$85.80
Purchase #7	$103.26	7.714%	$111.2255	$111.23	$111.25	$111.20
7 purchase totals =	$838.38		$914.9007	$914.90	$914.90	$915.00