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	$195.36	13.866%	$222.4486	$222.45	$222.45	$222.40
Purchase #2	$234.57	8.829%	$255.2802	$255.28	$255.30	$255.30
Purchase #3	$51.98	5.841%	$55.0162	$55.02	$55.00	$55.00
Purchase #4	$160.47	7.147%	$171.9388	$171.94	$171.95	$171.90
Purchase #5	$44.48	4.323%	$46.4029	$46.40	$46.40	$46.40
Purchase #6	$46.88	9.406%	$51.2895	$51.29	$51.30	$51.30
Purchase #7	$57.75	12.122%	$64.7505	$64.75	$64.75	$64.80
7 purchase totals =	$791.49		$867.1267	$867.13	$867.15	$867.10