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	$198.92	4.371%	$207.6148	$207.61	$207.60	$207.60
Purchase #2	$171.64	9.179%	$187.3948	$187.39	$187.40	$187.40
Purchase #3	$127.26	3.206%	$131.34	$131.34	$131.35	$131.30
Purchase #4	$246.81	13.420%	$279.9319	$279.93	$279.95	$279.90
Purchase #5	$88.94	10.796%	$98.542	$98.54	$98.55	$98.50
Purchase #6	$242.82	13.425%	$275.4186	$275.42	$275.40	$275.40
Purchase #7	$145.74	4.801%	$152.737	$152.74	$152.75	$152.70
7 purchase totals =	$1,222.13		$1,332.9791	$1,332.97	$1,333.00	$1,332.80