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	$140.27	6.116%	$148.8489	$148.85	$148.85	$148.80
Purchase #2	$90.81	8.719%	$98.7277	$98.73	$98.75	$98.70
Purchase #3	$31.59	11.602%	$35.2551	$35.26	$35.25	$35.30
Purchase #4	$165.73	10.354%	$182.8897	$182.89	$182.90	$182.90
Purchase #5	$167.54	11.636%	$187.035	$187.04	$187.05	$187.00
Purchase #6	$235.54	3.321%	$243.3623	$243.36	$243.35	$243.40
Purchase #7	$151.32	13.567%	$171.8496	$171.85	$171.85	$171.80
7 purchase totals =	$982.80		$1,067.9683	$1,067.98	$1,068.00	$1,067.90