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	$102.67	9.685%	$112.6136	$112.61	$112.60	$112.60
Purchase #2	$152.64	9.750%	$167.5224	$167.52	$167.50	$167.50
Purchase #3	$135.42	9.685%	$148.5354	$148.54	$148.55	$148.50
Purchase #4	$165.44	4.494%	$172.8749	$172.87	$172.85	$172.90
Purchase #5	$239.90	10.320%	$264.6577	$264.66	$264.65	$264.70
Purchase #6	$114.39	10.605%	$126.5211	$126.52	$126.50	$126.50
Purchase #7	$97.58	5.217%	$102.6707	$102.67	$102.65	$102.70
7 purchase totals =	$1,008.04		$1,095.3958	$1,095.39	$1,095.30	$1,095.40