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	$113.66	12.647%	$128.0346	$128.03	$128.05	$128.00
Purchase #2	$150.44	9.544%	$164.798	$164.80	$164.80	$164.80
Purchase #3	$156.54	11.376%	$174.348	$174.35	$174.35	$174.30
Purchase #4	$237.41	8.225%	$256.937	$256.94	$256.95	$256.90
Purchase #5	$105.80	5.387%	$111.4994	$111.50	$111.50	$111.50
Purchase #6	$182.59	5.183%	$192.0536	$192.05	$192.05	$192.10
Purchase #7	$147.76	11.344%	$164.5219	$164.52	$164.50	$164.50
7 purchase totals =	$1,094.20		$1,192.1925	$1,192.19	$1,192.20	$1,192.10