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	$81.90	8.147%	$88.5724	$88.57	$88.55	$88.60
Purchase #2	$208.72	13.447%	$236.7866	$236.79	$236.80	$236.80
Purchase #3	$41.28	3.141%	$42.5766	$42.58	$42.60	$42.60
Purchase #4	$215.37	9.653%	$236.1597	$236.16	$236.15	$236.20
Purchase #5	$177.98	5.382%	$187.5589	$187.56	$187.55	$187.60
Purchase #6	$86.34	11.692%	$96.4349	$96.43	$96.45	$96.40
Purchase #7	$243.27	5.326%	$256.2266	$256.23	$256.25	$256.20
7 purchase totals =	$1,054.86		$1,144.3157	$1,144.32	$1,144.35	$1,144.40