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	$92.94	12.561%	$104.6142	$104.61	$104.60	$104.60
Purchase #2	$172.77	8.740%	$187.8701	$187.87	$187.85	$187.90
Purchase #3	$67.99	6.826%	$72.631	$72.63	$72.65	$72.60
Purchase #4	$89.54	12.800%	$101.0011	$101.00	$101.00	$101.00
Purchase #5	$89.69	6.200%	$95.2508	$95.25	$95.25	$95.30
Purchase #6	$78.97	8.858%	$85.9652	$85.97	$85.95	$86.00
Purchase #7	$31.60	12.263%	$35.4751	$35.48	$35.50	$35.50
7 purchase totals =	$623.50		$682.8075	$682.81	$682.80	$682.90