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	$227.86	8.638%	$247.5425	$247.54	$247.55	$247.50
Purchase #2	$96.47	7.254%	$103.4679	$103.47	$103.45	$103.50
Purchase #3	$130.88	8.293%	$141.7339	$141.73	$141.75	$141.70
Purchase #4	$154.25	8.473%	$167.3196	$167.32	$167.30	$167.30
Purchase #5	$18.98	13.423%	$21.5277	$21.53	$21.55	$21.50
Purchase #6	$204.85	8.637%	$222.5429	$222.54	$222.55	$222.50
Purchase #7	$163.88	4.305%	$170.935	$170.94	$170.95	$170.90
7 purchase totals =	$997.17		$1,075.0695	$1,075.07	$1,075.10	$1,074.90