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	$192.69	11.803%	$215.4332	$215.43	$215.45	$215.40
Purchase #2	$63.35	5.145%	$66.6094	$66.61	$66.60	$66.60
Purchase #3	$53.98	9.619%	$59.1723	$59.17	$59.15	$59.20
Purchase #4	$37.52	13.786%	$42.6925	$42.69	$42.70	$42.70
Purchase #5	$13.47	7.210%	$14.4412	$14.44	$14.45	$14.40
Purchase #6	$205.82	5.372%	$216.8767	$216.88	$216.90	$216.90
Purchase #7	$209.66	9.568%	$229.7203	$229.72	$229.70	$229.70
7 purchase totals =	$776.49		$844.9456	$844.94	$844.95	$844.90