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	$121.66	8.405%	$131.8855	$131.89	$131.90	$131.90
Purchase #2	$209.92	11.746%	$234.5772	$234.58	$234.60	$234.60
Purchase #3	$208.82	7.487%	$224.4544	$224.45	$224.45	$224.50
Purchase #4	$51.64	8.699%	$56.1322	$56.13	$56.15	$56.10
Purchase #5	$99.25	10.570%	$109.7407	$109.74	$109.75	$109.70
Purchase #6	$78.93	13.791%	$89.8152	$89.82	$89.80	$89.80
Purchase #7	$186.37	10.482%	$205.9053	$205.91	$205.90	$205.90
7 purchase totals =	$956.59		$1,052.5105	$1,052.52	$1,052.55	$1,052.50