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	$246.60	13.432%	$279.7233	$279.72	$279.70	$279.70
Purchase #2	$191.38	10.144%	$210.7936	$210.79	$210.80	$210.80
Purchase #3	$155.59	4.719%	$162.9323	$162.93	$162.95	$162.90
Purchase #4	$37.57	13.150%	$42.5105	$42.51	$42.50	$42.50
Purchase #5	$51.51	5.639%	$54.4146	$54.41	$54.40	$54.40
Purchase #6	$15.89	13.807%	$18.0839	$18.08	$18.10	$18.10
Purchase #7	$228.85	11.794%	$255.8406	$255.84	$255.85	$255.80
7 purchase totals =	$927.39		$1,024.2988	$1,024.28	$1,024.30	$1,024.20