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	$190.71	10.396%	$210.5362	$210.54	$210.55	$210.50
Purchase #2	$79.82	7.794%	$86.0412	$86.04	$86.05	$86.00
Purchase #3	$172.33	10.294%	$190.0697	$190.07	$190.05	$190.10
Purchase #4	$190.35	3.825%	$197.6309	$197.63	$197.65	$197.60
Purchase #5	$119.60	11.252%	$133.0574	$133.06	$133.05	$133.10
Purchase #6	$87.52	3.414%	$90.5079	$90.51	$90.50	$90.50
Purchase #7	$241.42	13.582%	$274.2097	$274.21	$274.20	$274.20
7 purchase totals =	$1,081.75		$1,182.0530	$1,182.06	$1,182.05	$1,182.00