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	$160.55	13.581%	$182.3543	$182.35	$182.35	$182.40
Purchase #2	$62.97	6.362%	$66.9762	$66.98	$67.00	$67.00
Purchase #3	$215.45	4.165%	$224.4235	$224.42	$224.40	$224.40
Purchase #4	$229.69	11.594%	$256.3203	$256.32	$256.30	$256.30
Purchase #5	$50.66	9.184%	$55.3126	$55.31	$55.30	$55.30
Purchase #6	$183.65	6.732%	$196.0133	$196.01	$196.00	$196.00
Purchase #7	$46.62	5.494%	$49.1813	$49.18	$49.20	$49.20
7 purchase totals =	$949.59		$1,030.5815	$1,030.57	$1,030.55	$1,030.60