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	$244.60	5.151%	$257.1993	$257.20	$257.20	$257.20
Purchase #2	$91.52	8.709%	$99.4905	$99.49	$99.50	$99.50
Purchase #3	$95.54	6.639%	$101.8829	$101.88	$101.90	$101.90
Purchase #4	$137.71	8.865%	$149.918	$149.92	$149.90	$149.90
Purchase #5	$33.83	6.121%	$35.9007	$35.90	$35.90	$35.90
Purchase #6	$46.89	3.532%	$48.5462	$48.55	$48.55	$48.50
Purchase #7	$153.47	9.653%	$168.2845	$168.28	$168.30	$168.30
7 purchase totals =	$803.56		$861.2221	$861.22	$861.25	$861.20