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	$235.97	6.323%	$250.8904	$250.89	$250.90	$250.90
Purchase #2	$84.76	3.698%	$87.8944	$87.89	$87.90	$87.90
Purchase #3	$7.95	13.412%	$9.0163	$9.02	$9.00	$9.00
Purchase #4	$241.59	13.107%	$273.2552	$273.26	$273.25	$273.30
Purchase #5	$39.66	8.170%	$42.9002	$42.90	$42.90	$42.90
Purchase #6	$147.85	7.210%	$158.51	$158.51	$158.50	$158.50
Purchase #7	$171.94	12.745%	$193.8538	$193.85	$193.85	$193.90
7 purchase totals =	$929.72		$1,016.3203	$1,016.32	$1,016.30	$1,016.40