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	$202.90	4.243%	$211.509	$211.51	$211.50	$211.50
Purchase #2	$109.89	6.851%	$117.4186	$117.42	$117.40	$117.40
Purchase #3	$133.75	6.849%	$142.9105	$142.91	$142.90	$142.90
Purchase #4	$167.31	6.142%	$177.5862	$177.59	$177.60	$177.60
Purchase #5	$143.62	7.426%	$154.2852	$154.29	$154.30	$154.30
Purchase #6	$86.59	10.298%	$95.507	$95.51	$95.50	$95.50
Purchase #7	$64.53	11.652%	$72.049	$72.05	$72.05	$72.00
7 purchase totals =	$908.59		$971.2655	$971.28	$971.25	$971.20