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	$66.32	7.238%	$71.1202	$71.12	$71.10	$71.10
Purchase #2	$27.57	5.170%	$28.9954	$29.00	$29.00	$29.00
Purchase #3	$164.98	5.760%	$174.4828	$174.48	$174.50	$174.50
Purchase #4	$59.28	11.497%	$66.0954	$66.10	$66.10	$66.10
Purchase #5	$236.55	7.103%	$253.3521	$253.35	$253.35	$253.40
Purchase #6	$16.51	12.449%	$18.5653	$18.57	$18.55	$18.60
Purchase #7	$246.56	4.707%	$258.1656	$258.17	$258.15	$258.20
7 purchase totals =	$817.77		$870.7768	$870.79	$870.75	$870.90