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	$181.76	4.836%	$190.5499	$190.55	$190.55	$190.50
Purchase #2	$189.60	12.268%	$212.8601	$212.86	$212.85	$212.90
Purchase #3	$93.90	6.565%	$100.0645	$100.06	$100.05	$100.10
Purchase #4	$100.67	5.525%	$106.232	$106.23	$106.25	$106.20
Purchase #5	$122.50	3.121%	$126.3232	$126.32	$126.30	$126.30
Purchase #6	$33.56	6.692%	$35.8058	$35.81	$35.80	$35.80
Purchase #7	$217.54	13.225%	$246.3097	$246.31	$246.30	$246.30
7 purchase totals =	$939.53		$1,018.1452	$1,018.14	$1,018.10	$1,018.10