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	$65.29	13.118%	$73.8547	$73.85	$73.85	$73.90
Purchase #2	$95.82	13.349%	$108.611	$108.61	$108.60	$108.60
Purchase #3	$161.94	6.153%	$171.9042	$171.90	$171.90	$171.90
Purchase #4	$130.28	10.770%	$144.3112	$144.31	$144.30	$144.30
Purchase #5	$183.79	4.670%	$192.373	$192.37	$192.35	$192.40
Purchase #6	$41.53	5.525%	$43.8245	$43.82	$43.80	$43.80
Purchase #7	$161.25	13.690%	$183.3251	$183.33	$183.35	$183.30
7 purchase totals =	$839.90		$918.2037	$918.19	$918.15	$918.20