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	$92.89	7.218%	$99.5948	$99.59	$99.60	$99.60
Purchase #2	$104.97	13.377%	$119.0118	$119.01	$119.00	$119.00
Purchase #3	$66.42	7.540%	$71.4281	$71.43	$71.45	$71.40
Purchase #4	$242.61	3.569%	$251.2688	$251.27	$251.25	$251.30
Purchase #5	$62.27	4.184%	$64.8754	$64.88	$64.90	$64.90
Purchase #6	$228.84	4.713%	$239.6252	$239.63	$239.65	$239.60
Purchase #7	$239.31	8.315%	$259.2086	$259.21	$259.20	$259.20
7 purchase totals =	$1,037.31		$1,105.0127	$1,105.02	$1,105.05	$1,105.00