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	$195.79	7.534%	$210.5408	$210.54	$210.55	$210.50
Purchase #2	$73.53	7.301%	$78.8984	$78.90	$78.90	$78.90
Purchase #3	$232.48	11.632%	$259.5221	$259.52	$259.50	$259.50
Purchase #4	$115.62	6.576%	$123.2232	$123.22	$123.20	$123.20
Purchase #5	$160.82	9.697%	$176.4147	$176.41	$176.40	$176.40
Purchase #6	$218.25	13.457%	$247.6199	$247.62	$247.60	$247.60
Purchase #7	$154.31	5.567%	$162.9004	$162.90	$162.90	$162.90
7 purchase totals =	$1,150.80		$1,259.1195	$1,259.11	$1,259.05	$1,259.00