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	$122.83	7.294%	$131.7892	$131.79	$131.80	$131.80
Purchase #2	$64.75	13.787%	$73.6771	$73.68	$73.70	$73.70
Purchase #3	$153.45	10.705%	$169.8768	$169.88	$169.90	$169.90
Purchase #4	$168.48	8.855%	$183.3989	$183.40	$183.40	$183.40
Purchase #5	$136.59	5.731%	$144.418	$144.42	$144.40	$144.40
Purchase #6	$174.45	5.311%	$183.715	$183.72	$183.70	$183.70
Purchase #7	$191.65	11.205%	$213.1244	$213.12	$213.10	$213.10
7 purchase totals =	$1,012.20		$1,099.9994	$1,100.01	$1,100.00	$1,100.00