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	$142.79	7.563%	$153.5892	$153.59	$153.60	$153.60
Purchase #2	$103.96	7.594%	$111.8547	$111.85	$111.85	$111.90
Purchase #3	$213.43	13.309%	$241.8354	$241.84	$241.85	$241.80
Purchase #4	$184.89	7.442%	$198.6495	$198.65	$198.65	$198.60
Purchase #5	$239.53	11.873%	$267.9694	$267.97	$267.95	$268.00
Purchase #6	$199.61	3.111%	$205.8199	$205.82	$205.80	$205.80
Purchase #7	$109.25	9.233%	$119.3371	$119.34	$119.35	$119.30
7 purchase totals =	$1,193.46		$1,299.0552	$1,299.06	$1,299.05	$1,299.00