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	$118.92	5.665%	$125.6568	$125.66	$125.65	$125.70
Purchase #2	$156.36	9.543%	$171.2814	$171.28	$171.30	$171.30
Purchase #3	$41.61	9.255%	$45.461	$45.46	$45.45	$45.50
Purchase #4	$58.96	12.151%	$66.1242	$66.12	$66.10	$66.10
Purchase #5	$59.30	6.745%	$63.2998	$63.30	$63.30	$63.30
Purchase #6	$139.93	8.393%	$151.6743	$151.67	$151.65	$151.70
Purchase #7	$93.53	7.278%	$100.3371	$100.34	$100.35	$100.30
7 purchase totals =	$668.61		$723.8346	$723.83	$723.80	$723.90