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	$238.71	11.272%	$265.6174	$265.62	$265.60	$265.60
Purchase #2	$237.89	13.592%	$270.224	$270.22	$270.20	$270.20
Purchase #3	$42.95	7.533%	$46.1854	$46.19	$46.20	$46.20
Purchase #4	$133.79	13.764%	$152.2049	$152.20	$152.20	$152.20
Purchase #5	$56.25	8.472%	$61.0155	$61.02	$61.00	$61.00
Purchase #6	$95.77	7.405%	$102.8618	$102.86	$102.85	$102.90
Purchase #7	$108.64	7.605%	$116.9021	$116.90	$116.90	$116.90
7 purchase totals =	$914.00		$1,015.0111	$1,015.01	$1,014.95	$1,015.00