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	$217.94	12.697%	$245.6118	$245.61	$245.60	$245.60
Purchase #2	$166.49	13.246%	$188.5433	$188.54	$188.55	$188.50
Purchase #3	$63.85	9.140%	$69.6859	$69.69	$69.70	$69.70
Purchase #4	$152.60	11.304%	$169.8499	$169.85	$169.85	$169.80
Purchase #5	$99.51	3.780%	$103.2715	$103.27	$103.25	$103.30
Purchase #6	$151.72	13.263%	$171.8426	$171.84	$171.85	$171.80
Purchase #7	$108.48	12.809%	$122.3752	$122.38	$122.40	$122.40
7 purchase totals =	$960.59		$1,071.1802	$1,071.18	$1,071.20	$1,071.10