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	$6.46	9.631%	$7.0822	$7.08	$7.10	$7.10
Purchase #2	$56.68	4.169%	$59.043	$59.04	$59.05	$59.00
Purchase #3	$165.70	12.111%	$185.7679	$185.77	$185.75	$185.80
Purchase #4	$35.36	8.402%	$38.3309	$38.33	$38.35	$38.30
Purchase #5	$69.32	5.628%	$73.2213	$73.22	$73.20	$73.20
Purchase #6	$81.96	4.205%	$85.4064	$85.41	$85.40	$85.40
Purchase #7	$111.43	4.152%	$116.0566	$116.06	$116.05	$116.10
7 purchase totals =	$526.91		$564.9083	$564.91	$564.90	$564.90