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	$213.34	5.518%	$225.1121	$225.11	$225.10	$225.10
Purchase #2	$36.51	3.126%	$37.6513	$37.65	$37.65	$37.70
Purchase #3	$138.69	4.507%	$144.9408	$144.94	$144.95	$144.90
Purchase #4	$158.81	6.676%	$169.4122	$169.41	$169.40	$169.40
Purchase #5	$91.70	10.151%	$101.0085	$101.01	$101.00	$101.00
Purchase #6	$131.59	6.330%	$139.9196	$139.92	$139.90	$139.90
Purchase #7	$247.59	4.585%	$258.942	$258.94	$258.95	$258.90
7 purchase totals =	$1,018.23		$1,076.9865	$1,076.98	$1,076.95	$1,076.90