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	$248.69	10.103%	$273.8152	$273.82	$273.80	$273.80
Purchase #2	$90.57	9.219%	$98.9196	$98.92	$98.90	$98.90
Purchase #3	$243.86	3.855%	$253.2608	$253.26	$253.25	$253.30
Purchase #4	$20.90	3.423%	$21.6154	$21.62	$21.60	$21.60
Purchase #5	$225.92	6.383%	$240.3405	$240.34	$240.35	$240.30
Purchase #6	$99.68	12.167%	$111.8081	$111.81	$111.80	$111.80
Purchase #7	$70.74	7.451%	$76.0108	$76.01	$76.00	$76.00
7 purchase totals =	$1,000.36		$1,075.7704	$1,075.78	$1,075.70	$1,075.70