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	$66.33	9.361%	$72.5392	$72.54	$72.55	$72.50
Purchase #2	$243.66	12.870%	$275.019	$275.02	$275.00	$275.00
Purchase #3	$193.71	13.682%	$220.2134	$220.21	$220.20	$220.20
Purchase #4	$112.82	4.750%	$118.179	$118.18	$118.20	$118.20
Purchase #5	$174.40	12.613%	$196.3971	$196.40	$196.40	$196.40
Purchase #6	$190.90	13.850%	$217.3397	$217.34	$217.35	$217.30
Purchase #7	$101.74	3.757%	$105.5624	$105.56	$105.55	$105.60
7 purchase totals =	$1,083.56		$1,205.2498	$1,205.25	$1,205.25	$1,205.20