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	$117.95	6.236%	$125.3054	$125.31	$125.30	$125.30
Purchase #2	$102.66	10.534%	$113.4742	$113.47	$113.45	$113.50
Purchase #3	$168.56	3.211%	$173.9725	$173.97	$173.95	$174.00
Purchase #4	$242.42	8.248%	$262.4148	$262.41	$262.40	$262.40
Purchase #5	$236.94	11.477%	$264.1336	$264.13	$264.15	$264.10
Purchase #6	$104.65	9.371%	$114.4568	$114.46	$114.45	$114.50
Purchase #7	$131.86	8.242%	$142.7279	$142.73	$142.75	$142.70
7 purchase totals =	$1,105.04		$1,196.4852	$1,196.48	$1,196.45	$1,196.50