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	$170.29	5.284%	$179.2881	$179.29	$179.30	$179.30
Purchase #2	$176.87	8.632%	$192.1374	$192.14	$192.15	$192.10
Purchase #3	$64.73	12.602%	$72.8873	$72.89	$72.90	$72.90
Purchase #4	$136.62	11.483%	$152.3081	$152.31	$152.30	$152.30
Purchase #5	$204.29	10.573%	$225.8896	$225.89	$225.90	$225.90
Purchase #6	$198.27	7.676%	$213.4892	$213.49	$213.50	$213.50
Purchase #7	$69.94	7.688%	$75.317	$75.32	$75.30	$75.30
7 purchase totals =	$1,021.01		$1,111.3167	$1,111.33	$1,111.35	$1,111.30