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	$220.59	5.279%	$232.2349	$232.23	$232.25	$232.20
Purchase #2	$200.55	13.118%	$226.8581	$226.86	$226.85	$226.90
Purchase #3	$66.59	10.507%	$73.5866	$73.59	$73.60	$73.60
Purchase #4	$117.96	8.221%	$127.6575	$127.66	$127.65	$127.70
Purchase #5	$198.81	4.165%	$207.0904	$207.09	$207.10	$207.10
Purchase #6	$162.89	5.759%	$172.2708	$172.27	$172.25	$172.30
Purchase #7	$118.97	3.479%	$123.109	$123.11	$123.10	$123.10
7 purchase totals =	$1,086.36		$1,162.8073	$1,162.81	$1,162.80	$1,162.90