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	$18.42	7.764%	$19.8501	$19.85	$19.85	$19.90
Purchase #2	$61.44	10.306%	$67.772	$67.77	$67.75	$67.80
Purchase #3	$218.44	10.485%	$241.3434	$241.34	$241.35	$241.30
Purchase #4	$76.43	3.355%	$78.9942	$78.99	$79.00	$79.00
Purchase #5	$102.79	10.520%	$113.6035	$113.60	$113.60	$113.60
Purchase #6	$79.34	5.402%	$83.6259	$83.63	$83.65	$83.60
Purchase #7	$117.55	8.298%	$127.3043	$127.30	$127.30	$127.30
7 purchase totals =	$674.41		$732.4934	$732.48	$732.50	$732.50