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	$55.33	4.248%	$57.6804	$57.68	$57.70	$57.70
Purchase #2	$190.97	4.795%	$200.127	$200.13	$200.15	$200.10
Purchase #3	$107.54	7.762%	$115.8873	$115.89	$115.90	$115.90
Purchase #4	$70.92	11.211%	$78.8708	$78.87	$78.85	$78.90
Purchase #5	$89.53	11.214%	$99.5699	$99.57	$99.55	$99.60
Purchase #6	$7.59	8.727%	$8.2524	$8.25	$8.25	$8.30
Purchase #7	$190.84	12.671%	$215.0213	$215.02	$215.00	$215.00
7 purchase totals =	$712.72		$775.4091	$775.41	$775.40	$775.50