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	$237.90	11.679%	$265.6843	$265.68	$265.70	$265.70
Purchase #2	$102.90	9.182%	$112.3483	$112.35	$112.35	$112.30
Purchase #3	$225.46	11.230%	$250.7792	$250.78	$250.80	$250.80
Purchase #4	$101.91	3.840%	$105.8233	$105.82	$105.80	$105.80
Purchase #5	$41.43	11.509%	$46.1982	$46.20	$46.20	$46.20
Purchase #6	$172.56	6.667%	$184.0646	$184.06	$184.05	$184.10
Purchase #7	$191.26	3.535%	$198.021	$198.02	$198.00	$198.00
7 purchase totals =	$1,073.42		$1,162.9189	$1,162.91	$1,162.90	$1,162.90