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	$237.61	7.726%	$255.9677	$255.97	$255.95	$256.00
Purchase #2	$152.78	10.202%	$168.3666	$168.37	$168.35	$168.40
Purchase #3	$96.42	5.402%	$101.6286	$101.63	$101.65	$101.60
Purchase #4	$52.86	11.616%	$59.0002	$59.00	$59.00	$59.00
Purchase #5	$207.32	12.459%	$233.15	$233.15	$233.15	$233.20
Purchase #6	$64.38	10.856%	$71.3691	$71.37	$71.35	$71.40
Purchase #7	$238.29	8.536%	$258.6304	$258.63	$258.65	$258.60
7 purchase totals =	$1,049.66		$1,148.1126	$1,148.12	$1,148.10	$1,148.20