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	$12.83	11.661%	$14.3261	$14.33	$14.35	$14.30
Purchase #2	$83.27	7.778%	$89.7467	$89.75	$89.75	$89.70
Purchase #3	$123.70	8.503%	$134.2182	$134.22	$134.20	$134.20
Purchase #4	$6.90	8.496%	$7.4862	$7.49	$7.50	$7.50
Purchase #5	$22.71	12.829%	$25.6235	$25.62	$25.60	$25.60
Purchase #6	$40.52	6.413%	$43.1185	$43.12	$43.10	$43.10
Purchase #7	$172.40	5.226%	$181.4096	$181.41	$181.40	$181.40
7 purchase totals =	$462.33		$495.9288	$495.94	$495.90	$495.80