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	$106.56	6.272%	$113.2434	$113.24	$113.25	$113.20
Purchase #2	$24.93	10.126%	$27.4544	$27.45	$27.45	$27.50
Purchase #3	$186.82	5.241%	$196.6112	$196.61	$196.60	$196.60
Purchase #4	$189.54	9.779%	$208.0751	$208.08	$208.10	$208.10
Purchase #5	$102.42	6.760%	$109.3436	$109.34	$109.35	$109.30
Purchase #6	$207.89	13.579%	$236.1194	$236.12	$236.10	$236.10
Purchase #7	$130.98	5.135%	$137.7058	$137.71	$137.70	$137.70
7 purchase totals =	$949.14		$1,028.5529	$1,028.55	$1,028.55	$1,028.50