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	$58.76	3.750%	$60.9635	$60.96	$60.95	$61.00
Purchase #2	$250.36	6.503%	$266.6409	$266.64	$266.65	$266.60
Purchase #3	$227.67	4.746%	$238.4752	$238.48	$238.50	$238.50
Purchase #4	$229.59	11.297%	$255.5268	$255.53	$255.55	$255.50
Purchase #5	$80.89	3.256%	$83.5238	$83.52	$83.50	$83.50
Purchase #6	$44.63	10.336%	$49.243	$49.24	$49.25	$49.20
Purchase #7	$51.57	9.745%	$56.5955	$56.60	$56.60	$56.60
7 purchase totals =	$943.47		$1,010.9687	$1,010.97	$1,011.00	$1,010.90