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	$242.34	5.648%	$256.0274	$256.03	$256.05	$256.00
Purchase #2	$12.50	10.153%	$13.7691	$13.77	$13.75	$13.80
Purchase #3	$161.78	4.293%	$168.7252	$168.73	$168.75	$168.70
Purchase #4	$124.67	12.626%	$140.4108	$140.41	$140.40	$140.40
Purchase #5	$111.56	11.127%	$123.9733	$123.97	$123.95	$124.00
Purchase #6	$187.35	11.581%	$209.047	$209.05	$209.05	$209.00
Purchase #7	$91.30	9.234%	$99.7306	$99.73	$99.75	$99.70
7 purchase totals =	$931.50		$1,011.6834	$1,011.69	$1,011.70	$1,011.60