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	$182.96	4.408%	$191.0249	$191.02	$191.00	$191.00
Purchase #2	$54.59	3.862%	$56.6983	$56.70	$56.70	$56.70
Purchase #3	$180.59	10.717%	$199.9438	$199.94	$199.95	$199.90
Purchase #4	$116.38	7.826%	$125.4879	$125.49	$125.50	$125.50
Purchase #5	$227.85	12.125%	$255.4768	$255.48	$255.50	$255.50
Purchase #6	$61.55	12.308%	$69.1256	$69.13	$69.15	$69.10
Purchase #7	$73.78	9.233%	$80.5921	$80.59	$80.60	$80.60
7 purchase totals =	$897.70		$978.3494	$978.35	$978.40	$978.30