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	$82.37	11.483%	$91.8285	$91.83	$91.85	$91.80
Purchase #2	$79.33	7.708%	$85.4448	$85.44	$85.45	$85.40
Purchase #3	$40.27	8.121%	$43.5403	$43.54	$43.55	$43.50
Purchase #4	$149.40	12.644%	$168.2901	$168.29	$168.30	$168.30
Purchase #5	$200.69	10.407%	$221.5758	$221.58	$221.60	$221.60
Purchase #6	$130.82	6.532%	$139.3652	$139.37	$139.35	$139.40
Purchase #7	$102.25	13.536%	$116.0906	$116.09	$116.10	$116.10
7 purchase totals =	$785.13		$866.1353	$866.14	$866.20	$866.10