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	$144.94	5.243%	$152.5392	$152.54	$152.55	$152.50
Purchase #2	$39.80	6.832%	$42.5191	$42.52	$42.50	$42.50
Purchase #3	$168.34	6.338%	$179.0094	$179.01	$179.00	$179.00
Purchase #4	$172.91	4.619%	$180.8967	$180.90	$180.90	$180.90
Purchase #5	$47.31	6.205%	$50.2456	$50.25	$50.25	$50.20
Purchase #6	$112.79	6.631%	$120.2691	$120.27	$120.25	$120.30
Purchase #7	$34.32	3.154%	$35.4025	$35.40	$35.40	$35.40
7 purchase totals =	$720.41		$760.8816	$760.89	$760.85	$760.80