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	$64.99	9.861%	$71.3987	$71.40	$71.40	$71.40
Purchase #2	$133.86	9.398%	$146.4402	$146.44	$146.45	$146.40
Purchase #3	$123.94	3.314%	$128.0474	$128.05	$128.05	$128.00
Purchase #4	$224.29	13.643%	$254.8899	$254.89	$254.90	$254.90
Purchase #5	$143.49	3.566%	$148.6069	$148.61	$148.60	$148.60
Purchase #6	$198.84	6.431%	$211.6274	$211.63	$211.65	$211.60
Purchase #7	$49.70	10.870%	$55.1024	$55.10	$55.10	$55.10
7 purchase totals =	$939.11		$1,016.1129	$1,016.12	$1,016.15	$1,016.00