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	$118.30	8.336%	$128.1615	$128.16	$128.15	$128.20
Purchase #2	$38.79	12.738%	$43.7311	$43.73	$43.75	$43.70
Purchase #3	$239.30	4.425%	$249.889	$249.89	$249.90	$249.90
Purchase #4	$229.40	8.694%	$249.344	$249.34	$249.35	$249.30
Purchase #5	$56.72	7.745%	$61.113	$61.11	$61.10	$61.10
Purchase #6	$198.82	3.491%	$205.7608	$205.76	$205.75	$205.80
Purchase #7	$107.72	10.516%	$119.0478	$119.05	$119.05	$119.00
7 purchase totals =	$989.05		$1,057.0472	$1,057.04	$1,057.05	$1,057.00