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	$78.35	9.245%	$85.5935	$85.59	$85.60	$85.60
Purchase #2	$171.52	10.305%	$189.1951	$189.20	$189.20	$189.20
Purchase #3	$92.90	10.539%	$102.6907	$102.69	$102.70	$102.70
Purchase #4	$105.47	13.719%	$119.9394	$119.94	$119.95	$119.90
Purchase #5	$241.32	13.121%	$272.9836	$272.98	$273.00	$273.00
Purchase #6	$172.43	4.568%	$180.3066	$180.31	$180.30	$180.30
Purchase #7	$52.57	4.322%	$54.8421	$54.84	$54.85	$54.80
7 purchase totals =	$914.56		$1,005.5510	$1,005.55	$1,005.60	$1,005.50