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	$154.74	6.675%	$165.0689	$165.07	$165.05	$165.10
Purchase #2	$69.39	13.263%	$78.5932	$78.59	$78.60	$78.60
Purchase #3	$150.30	12.366%	$168.8861	$168.89	$168.90	$168.90
Purchase #4	$105.37	13.291%	$119.3747	$119.37	$119.35	$119.40
Purchase #5	$57.36	7.751%	$61.806	$61.81	$61.80	$61.80
Purchase #6	$221.52	7.402%	$237.9169	$237.92	$237.90	$237.90
Purchase #7	$200.99	6.117%	$213.2846	$213.28	$213.30	$213.30
7 purchase totals =	$959.67		$1,044.9304	$1,044.93	$1,044.90	$1,045.00