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	$238.92	9.381%	$261.3331	$261.33	$261.35	$261.30
Purchase #2	$189.40	13.830%	$215.594	$215.59	$215.60	$215.60
Purchase #3	$52.33	9.557%	$57.3312	$57.33	$57.35	$57.30
Purchase #4	$25.73	8.868%	$28.0117	$28.01	$28.00	$28.00
Purchase #5	$135.54	4.684%	$141.8887	$141.89	$141.90	$141.90
Purchase #6	$229.64	9.342%	$251.093	$251.09	$251.10	$251.10
Purchase #7	$208.36	10.536%	$230.3128	$230.31	$230.30	$230.30
7 purchase totals =	$1,079.92		$1,185.5645	$1,185.55	$1,185.60	$1,185.50