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	$228.60	6.109%	$242.5652	$242.57	$242.55	$242.60
Purchase #2	$94.45	6.339%	$100.4372	$100.44	$100.45	$100.40
Purchase #3	$103.86	12.694%	$117.044	$117.04	$117.05	$117.00
Purchase #4	$100.66	4.713%	$105.4041	$105.40	$105.40	$105.40
Purchase #5	$141.48	4.314%	$147.5834	$147.58	$147.60	$147.60
Purchase #6	$126.92	3.557%	$131.4345	$131.43	$131.45	$131.40
Purchase #7	$66.74	4.265%	$69.5865	$69.59	$69.60	$69.60
7 purchase totals =	$862.71		$914.0549	$914.05	$914.10	$914.00