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	$228.27	10.351%	$251.8982	$251.90	$251.90	$251.90
Purchase #2	$44.46	7.124%	$47.6273	$47.63	$47.65	$47.60
Purchase #3	$93.31	6.683%	$99.5459	$99.55	$99.55	$99.50
Purchase #4	$229.32	3.872%	$238.1993	$238.20	$238.20	$238.20
Purchase #5	$229.59	12.635%	$258.5987	$258.60	$258.60	$258.60
Purchase #6	$182.86	3.393%	$189.0644	$189.06	$189.05	$189.10
Purchase #7	$166.53	3.203%	$171.864	$171.86	$171.85	$171.90
7 purchase totals =	$1,174.34		$1,256.7978	$1,256.80	$1,256.80	$1,256.80