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	$162.63	5.767%	$172.0089	$172.01	$172.00	$172.00
Purchase #2	$130.91	8.155%	$141.5857	$141.59	$141.60	$141.60
Purchase #3	$7.31	4.258%	$7.6213	$7.62	$7.60	$7.60
Purchase #4	$172.87	5.553%	$182.4695	$182.47	$182.45	$182.50
Purchase #5	$206.41	4.303%	$215.2918	$215.29	$215.30	$215.30
Purchase #6	$164.85	7.264%	$176.8247	$176.82	$176.80	$176.80
Purchase #7	$79.26	12.482%	$89.1532	$89.15	$89.15	$89.20
7 purchase totals =	$924.24		$984.9551	$984.95	$984.90	$985.00