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	$219.81	12.826%	$248.0028	$248.00	$248.00	$248.00
Purchase #2	$155.80	8.173%	$168.5335	$168.53	$168.55	$168.50
Purchase #3	$140.70	12.618%	$158.4535	$158.45	$158.45	$158.50
Purchase #4	$63.84	4.779%	$66.8909	$66.89	$66.90	$66.90
Purchase #5	$179.92	4.842%	$188.6317	$188.63	$188.65	$188.60
Purchase #6	$164.64	3.716%	$170.758	$170.76	$170.75	$170.80
Purchase #7	$166.61	7.471%	$179.0574	$179.06	$179.05	$179.10
7 purchase totals =	$1,091.32		$1,180.3278	$1,180.32	$1,180.35	$1,180.40