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	$197.33	13.235%	$223.4466	$223.45	$223.45	$223.40
Purchase #2	$167.72	7.861%	$180.9045	$180.90	$180.90	$180.90
Purchase #3	$241.67	3.254%	$249.5339	$249.53	$249.55	$249.50
Purchase #4	$94.92	5.672%	$100.3039	$100.30	$100.30	$100.30
Purchase #5	$34.99	4.314%	$36.4995	$36.50	$36.50	$36.50
Purchase #6	$214.85	6.690%	$229.2235	$229.22	$229.20	$229.20
Purchase #7	$57.84	11.671%	$64.5905	$64.59	$64.60	$64.60
7 purchase totals =	$1,009.32		$1,084.5024	$1,084.49	$1,084.50	$1,084.40