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	$35.79	7.225%	$38.3758	$38.38	$38.40	$38.40
Purchase #2	$58.65	9.303%	$64.1062	$64.11	$64.10	$64.10
Purchase #3	$97.83	11.835%	$109.4082	$109.41	$109.40	$109.40
Purchase #4	$138.29	10.618%	$152.9736	$152.97	$152.95	$153.00
Purchase #5	$167.94	7.136%	$179.9242	$179.92	$179.90	$179.90
Purchase #6	$89.92	10.431%	$99.2996	$99.30	$99.30	$99.30
Purchase #7	$207.44	4.617%	$217.0175	$217.02	$217.00	$217.00
7 purchase totals =	$795.86		$861.1051	$861.11	$861.05	$861.10