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	$248.55	7.298%	$266.6892	$266.69	$266.70	$266.70
Purchase #2	$137.56	12.256%	$154.4194	$154.42	$154.40	$154.40
Purchase #3	$27.50	4.652%	$28.7793	$28.78	$28.80	$28.80
Purchase #4	$196.83	7.129%	$210.862	$210.86	$210.85	$210.90
Purchase #5	$40.46	11.222%	$45.0004	$45.00	$45.00	$45.00
Purchase #6	$219.91	4.734%	$230.3205	$230.32	$230.30	$230.30
Purchase #7	$237.76	13.751%	$270.4544	$270.45	$270.45	$270.50
7 purchase totals =	$1,108.57		$1,206.5252	$1,206.52	$1,206.50	$1,206.60