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	$156.81	11.127%	$174.2582	$174.26	$174.25	$174.30
Purchase #2	$176.84	8.649%	$192.1349	$192.13	$192.15	$192.10
Purchase #3	$64.94	9.196%	$70.9119	$70.91	$70.90	$70.90
Purchase #4	$169.29	9.507%	$185.3844	$185.38	$185.40	$185.40
Purchase #5	$126.25	11.345%	$140.5731	$140.57	$140.55	$140.60
Purchase #6	$156.36	10.557%	$172.8669	$172.87	$172.85	$172.90
Purchase #7	$117.73	10.641%	$130.2576	$130.26	$130.25	$130.30
7 purchase totals =	$968.22		$1,066.3870	$1,066.38	$1,066.35	$1,066.50