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	$152.67	8.436%	$165.5492	$165.55	$165.55	$165.50
Purchase #2	$105.96	11.794%	$118.4569	$118.46	$118.45	$118.50
Purchase #3	$198.35	11.558%	$221.2753	$221.28	$221.30	$221.30
Purchase #4	$149.79	8.396%	$162.3664	$162.37	$162.35	$162.40
Purchase #5	$9.73	8.829%	$10.5891	$10.59	$10.60	$10.60
Purchase #6	$86.30	5.709%	$91.2269	$91.23	$91.25	$91.20
Purchase #7	$60.58	8.184%	$65.5379	$65.54	$65.55	$65.50
7 purchase totals =	$763.38		$835.0017	$835.02	$835.05	$835.00