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	$200.63	10.807%	$222.3121	$222.31	$222.30	$222.30
Purchase #2	$164.94	4.651%	$172.6114	$172.61	$172.60	$172.60
Purchase #3	$63.44	10.471%	$70.0828	$70.08	$70.10	$70.10
Purchase #4	$211.53	4.618%	$221.2985	$221.30	$221.30	$221.30
Purchase #5	$143.46	7.212%	$153.8063	$153.81	$153.80	$153.80
Purchase #6	$174.81	4.421%	$182.5384	$182.54	$182.55	$182.50
Purchase #7	$200.29	11.328%	$222.9789	$222.98	$223.00	$223.00
7 purchase totals =	$1,159.10		$1,245.6284	$1,245.63	$1,245.65	$1,245.60