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	$160.90	12.659%	$181.2683	$181.27	$181.25	$181.30
Purchase #2	$38.69	3.846%	$40.178	$40.18	$40.20	$40.20
Purchase #3	$170.65	3.241%	$176.1808	$176.18	$176.20	$176.20
Purchase #4	$57.32	4.485%	$59.8908	$59.89	$59.90	$59.90
Purchase #5	$21.26	5.240%	$22.374	$22.37	$22.35	$22.40
Purchase #6	$152.91	4.750%	$160.1732	$160.17	$160.15	$160.20
Purchase #7	$60.62	11.776%	$67.7586	$67.76	$67.75	$67.80
7 purchase totals =	$662.35		$707.8237	$707.82	$707.80	$708.00