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	$157.27	9.570%	$172.3207	$172.32	$172.30	$172.30
Purchase #2	$249.72	12.365%	$280.5979	$280.60	$280.60	$280.60
Purchase #3	$164.68	4.391%	$171.9111	$171.91	$171.90	$171.90
Purchase #4	$234.31	9.311%	$256.1266	$256.13	$256.15	$256.10
Purchase #5	$64.83	10.334%	$71.5295	$71.53	$71.55	$71.50
Purchase #6	$118.65	6.456%	$126.31	$126.31	$126.30	$126.30
Purchase #7	$248.70	8.480%	$269.7898	$269.79	$269.80	$269.80
7 purchase totals =	$1,238.16		$1,348.5856	$1,348.59	$1,348.60	$1,348.50