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	$210.73	10.821%	$233.5331	$233.53	$233.55	$233.50
Purchase #2	$98.59	13.702%	$112.0988	$112.10	$112.10	$112.10
Purchase #3	$64.79	7.791%	$69.8378	$69.84	$69.85	$69.80
Purchase #4	$33.91	5.857%	$35.8961	$35.90	$35.90	$35.90
Purchase #5	$153.96	7.119%	$164.9204	$164.92	$164.90	$164.90
Purchase #6	$81.77	9.813%	$89.7941	$89.79	$89.80	$89.80
Purchase #7	$217.30	7.782%	$234.2103	$234.21	$234.20	$234.20
7 purchase totals =	$861.05		$940.2906	$940.29	$940.30	$940.20