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	$183.96	6.371%	$195.6801	$195.68	$195.70	$195.70
Purchase #2	$164.90	4.582%	$172.4557	$172.46	$172.45	$172.50
Purchase #3	$76.89	8.711%	$83.5879	$83.59	$83.60	$83.60
Purchase #4	$187.27	12.691%	$211.0364	$211.04	$211.05	$211.00
Purchase #5	$141.32	3.735%	$146.5983	$146.60	$146.60	$146.60
Purchase #6	$219.84	3.535%	$227.6113	$227.61	$227.60	$227.60
Purchase #7	$212.62	12.324%	$238.8233	$238.82	$238.80	$238.80
7 purchase totals =	$1,186.80		$1,275.7930	$1,275.80	$1,275.80	$1,275.80