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	$213.38	6.131%	$226.4623	$226.46	$226.45	$226.50
Purchase #2	$145.59	11.443%	$162.2499	$162.25	$162.25	$162.20
Purchase #3	$160.40	12.459%	$180.3842	$180.38	$180.40	$180.40
Purchase #4	$178.74	4.119%	$186.1023	$186.10	$186.10	$186.10
Purchase #5	$142.57	9.740%	$156.4563	$156.46	$156.45	$156.50
Purchase #6	$163.82	11.652%	$182.9083	$182.91	$182.90	$182.90
Purchase #7	$141.80	9.619%	$155.4397	$155.44	$155.45	$155.40
7 purchase totals =	$1,146.30		$1,250.0030	$1,250.00	$1,250.00	$1,250.00