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	$177.41	12.266%	$199.1711	$199.17	$199.15	$199.20
Purchase #2	$76.92	13.723%	$87.4757	$87.48	$87.50	$87.50
Purchase #3	$116.35	9.632%	$127.5568	$127.56	$127.55	$127.60
Purchase #4	$161.79	6.183%	$171.7935	$171.79	$171.80	$171.80
Purchase #5	$24.27	4.292%	$25.3117	$25.31	$25.30	$25.30
Purchase #6	$181.83	12.238%	$204.0824	$204.08	$204.10	$204.10
Purchase #7	$95.84	4.290%	$99.9515	$99.95	$99.95	$100.00
7 purchase totals =	$834.41		$915.3427	$915.34	$915.35	$915.50