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	$205.92	3.308%	$212.7318	$212.73	$212.75	$212.70
Purchase #2	$210.48	5.472%	$221.9975	$222.00	$222.00	$222.00
Purchase #3	$180.62	8.725%	$196.3791	$196.38	$196.40	$196.40
Purchase #4	$165.40	13.111%	$187.0856	$187.09	$187.10	$187.10
Purchase #5	$96.74	6.873%	$103.3889	$103.39	$103.40	$103.40
Purchase #6	$131.46	4.867%	$137.8582	$137.86	$137.85	$137.90
Purchase #7	$146.31	4.829%	$153.3753	$153.38	$153.40	$153.40
7 purchase totals =	$1,136.93		$1,212.8164	$1,212.83	$1,212.90	$1,212.90