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	$177.53	8.348%	$192.3502	$192.35	$192.35	$192.40
Purchase #2	$110.85	8.148%	$119.8821	$119.88	$119.90	$119.90
Purchase #3	$82.75	8.602%	$89.8682	$89.87	$89.85	$89.90
Purchase #4	$122.76	7.791%	$132.3242	$132.32	$132.30	$132.30
Purchase #5	$111.82	4.303%	$116.6316	$116.63	$116.65	$116.60
Purchase #6	$196.48	6.807%	$209.8544	$209.85	$209.85	$209.90
Purchase #7	$52.69	4.517%	$55.07	$55.07	$55.05	$55.10
7 purchase totals =	$854.88		$915.9807	$915.97	$915.95	$916.10