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	$40.65	7.324%	$43.6272	$43.63	$43.65	$43.60
Purchase #2	$42.81	8.311%	$46.3679	$46.37	$46.35	$46.40
Purchase #3	$41.93	10.405%	$46.2928	$46.29	$46.30	$46.30
Purchase #4	$89.67	11.207%	$99.7193	$99.72	$99.70	$99.70
Purchase #5	$75.77	13.342%	$85.8792	$85.88	$85.90	$85.90
Purchase #6	$134.47	10.431%	$148.4966	$148.50	$148.50	$148.50
Purchase #7	$58.44	12.708%	$65.8666	$65.87	$65.85	$65.90
7 purchase totals =	$483.74		$536.2496	$536.26	$536.25	$536.30