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	$76.50	4.757%	$80.1391	$80.14	$80.15	$80.10
Purchase #2	$117.78	4.553%	$123.1425	$123.14	$123.15	$123.10
Purchase #3	$206.63	4.826%	$216.602	$216.60	$216.60	$216.60
Purchase #4	$249.79	11.103%	$277.5242	$277.52	$277.50	$277.50
Purchase #5	$175.72	6.172%	$186.5654	$186.57	$186.55	$186.60
Purchase #6	$83.61	7.240%	$89.6634	$89.66	$89.65	$89.70
Purchase #7	$51.75	4.409%	$54.0317	$54.03	$54.05	$54.00
7 purchase totals =	$961.78		$1,027.6683	$1,027.66	$1,027.65	$1,027.60