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	$160.47	9.421%	$175.5879	$175.59	$175.60	$175.60
Purchase #2	$169.42	5.530%	$178.7889	$178.79	$178.80	$178.80
Purchase #3	$95.38	13.298%	$108.0636	$108.06	$108.05	$108.10
Purchase #4	$233.33	5.850%	$246.9798	$246.98	$247.00	$247.00
Purchase #5	$230.89	13.420%	$261.8754	$261.88	$261.90	$261.90
Purchase #6	$223.50	3.318%	$230.9157	$230.92	$230.90	$230.90
Purchase #7	$123.25	6.764%	$131.5866	$131.59	$131.60	$131.60
7 purchase totals =	$1,236.24		$1,333.7979	$1,333.81	$1,333.85	$1,333.90