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	$149.66	10.155%	$164.858	$164.86	$164.85	$164.90
Purchase #2	$142.94	13.382%	$162.0682	$162.07	$162.05	$162.10
Purchase #3	$31.44	12.302%	$35.3077	$35.31	$35.30	$35.30
Purchase #4	$91.80	13.295%	$104.0048	$104.00	$104.00	$104.00
Purchase #5	$133.25	7.265%	$142.9306	$142.93	$142.95	$142.90
Purchase #6	$70.27	4.734%	$73.5966	$73.60	$73.60	$73.60
Purchase #7	$126.88	11.824%	$141.8823	$141.88	$141.90	$141.90
7 purchase totals =	$746.24		$824.6482	$824.65	$824.65	$824.70