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	$102.68	9.749%	$112.6903	$112.69	$112.70	$112.70
Purchase #2	$18.34	6.181%	$19.4736	$19.47	$19.45	$19.50
Purchase #3	$62.82	5.540%	$66.3002	$66.30	$66.30	$66.30
Purchase #4	$161.46	13.425%	$183.136	$183.14	$183.15	$183.10
Purchase #5	$31.83	6.404%	$33.8684	$33.87	$33.85	$33.90
Purchase #6	$109.40	12.773%	$123.3737	$123.37	$123.35	$123.40
Purchase #7	$52.85	8.764%	$57.4818	$57.48	$57.50	$57.50
7 purchase totals =	$539.38		$596.3240	$596.32	$596.30	$596.40