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	$83.77	11.739%	$93.6038	$93.60	$93.60	$93.60
Purchase #2	$83.97	3.135%	$86.6025	$86.60	$86.60	$86.60
Purchase #3	$82.64	8.122%	$89.352	$89.35	$89.35	$89.40
Purchase #4	$92.67	12.796%	$104.5281	$104.53	$104.55	$104.50
Purchase #5	$113.54	4.715%	$118.8934	$118.89	$118.90	$118.90
Purchase #6	$52.82	3.724%	$54.787	$54.79	$54.80	$54.80
Purchase #7	$94.29	8.682%	$102.4763	$102.48	$102.50	$102.50
7 purchase totals =	$603.70		$650.2431	$650.24	$650.30	$650.30