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	$198.49	12.681%	$223.6605	$223.66	$223.65	$223.70
Purchase #2	$137.83	9.690%	$151.1857	$151.19	$151.20	$151.20
Purchase #3	$204.62	13.419%	$232.078	$232.08	$232.10	$232.10
Purchase #4	$205.25	5.301%	$216.1303	$216.13	$216.15	$216.10
Purchase #5	$46.69	10.504%	$51.5943	$51.59	$51.60	$51.60
Purchase #6	$119.90	3.360%	$123.9286	$123.93	$123.95	$123.90
Purchase #7	$78.89	4.620%	$82.5347	$82.53	$82.55	$82.50
7 purchase totals =	$991.67		$1,081.1121	$1,081.11	$1,081.20	$1,081.10