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	$57.75	6.752%	$61.6493	$61.65	$61.65	$61.60
Purchase #2	$171.32	9.812%	$188.1299	$188.13	$188.15	$188.10
Purchase #3	$5.75	12.423%	$6.4643	$6.46	$6.45	$6.50
Purchase #4	$91.97	9.523%	$100.7283	$100.73	$100.75	$100.70
Purchase #5	$162.53	6.563%	$173.1968	$173.20	$173.20	$173.20
Purchase #6	$181.55	8.161%	$196.3663	$196.37	$196.35	$196.40
Purchase #7	$127.71	10.650%	$141.3111	$141.31	$141.30	$141.30
7 purchase totals =	$798.58		$867.8460	$867.85	$867.85	$867.80