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	$113.31	11.636%	$126.4948	$126.49	$126.50	$126.50
Purchase #2	$28.74	11.311%	$31.9908	$31.99	$32.00	$32.00
Purchase #3	$119.77	7.559%	$128.8234	$128.82	$128.80	$128.80
Purchase #4	$157.91	9.220%	$172.4693	$172.47	$172.45	$172.50
Purchase #5	$45.68	6.170%	$48.4985	$48.50	$48.50	$48.50
Purchase #6	$233.94	5.219%	$246.1493	$246.15	$246.15	$246.10
Purchase #7	$171.83	9.446%	$188.0611	$188.06	$188.05	$188.10
7 purchase totals =	$871.18		$942.4872	$942.48	$942.45	$942.50