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	$210.27	5.653%	$222.1566	$222.16	$222.15	$222.20
Purchase #2	$50.72	4.266%	$52.8837	$52.88	$52.90	$52.90
Purchase #3	$69.93	5.153%	$73.5335	$73.53	$73.55	$73.50
Purchase #4	$117.69	6.566%	$125.4175	$125.42	$125.40	$125.40
Purchase #5	$237.25	3.746%	$246.1374	$246.14	$246.15	$246.10
Purchase #6	$240.47	6.282%	$255.5763	$255.58	$255.60	$255.60
Purchase #7	$156.36	7.124%	$167.4991	$167.50	$167.50	$167.50
7 purchase totals =	$1,082.69		$1,143.2041	$1,143.21	$1,143.25	$1,143.20