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	$228.73	11.638%	$255.3496	$255.35	$255.35	$255.30
Purchase #2	$229.51	8.698%	$249.4728	$249.47	$249.45	$249.50
Purchase #3	$162.61	7.357%	$174.5732	$174.57	$174.55	$174.60
Purchase #4	$73.73	12.597%	$83.0178	$83.02	$83.00	$83.00
Purchase #5	$232.56	4.658%	$243.3926	$243.39	$243.40	$243.40
Purchase #6	$98.95	3.593%	$102.5053	$102.51	$102.50	$102.50
Purchase #7	$153.68	3.372%	$158.8621	$158.86	$158.85	$158.90
7 purchase totals =	$1,179.77		$1,267.1734	$1,267.17	$1,267.10	$1,267.20