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	$100.67	6.530%	$107.2438	$107.24	$107.25	$107.20
Purchase #2	$244.34	4.624%	$255.6383	$255.64	$255.65	$255.60
Purchase #3	$219.69	3.765%	$227.9613	$227.96	$227.95	$228.00
Purchase #4	$104.83	6.293%	$111.427	$111.43	$111.45	$111.40
Purchase #5	$114.93	7.687%	$123.7647	$123.76	$123.75	$123.80
Purchase #6	$226.32	6.513%	$241.0602	$241.06	$241.05	$241.10
Purchase #7	$177.36	6.308%	$188.5479	$188.55	$188.55	$188.50
7 purchase totals =	$1,188.14		$1,255.6432	$1,255.64	$1,255.65	$1,255.60