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	$180.84	10.753%	$200.2857	$200.29	$200.30	$200.30
Purchase #2	$149.44	10.794%	$165.5706	$165.57	$165.55	$165.60
Purchase #3	$123.76	6.269%	$131.5185	$131.52	$131.50	$131.50
Purchase #4	$94.77	4.276%	$98.8224	$98.82	$98.80	$98.80
Purchase #5	$156.44	10.215%	$172.4203	$172.42	$172.40	$172.40
Purchase #6	$44.39	7.143%	$47.5608	$47.56	$47.55	$47.60
Purchase #7	$190.89	8.466%	$207.0507	$207.05	$207.05	$207.10
7 purchase totals =	$940.53		$1,023.2290	$1,023.23	$1,023.15	$1,023.30