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	$132.77	6.212%	$141.0177	$141.02	$141.00	$141.00
Purchase #2	$238.67	7.153%	$255.7421	$255.74	$255.75	$255.70
Purchase #3	$93.45	12.354%	$104.9948	$104.99	$105.00	$105.00
Purchase #4	$113.52	4.639%	$118.7862	$118.79	$118.80	$118.80
Purchase #5	$37.35	9.564%	$40.9222	$40.92	$40.90	$40.90
Purchase #6	$59.90	3.300%	$61.8767	$61.88	$61.90	$61.90
Purchase #7	$31.46	7.794%	$33.912	$33.91	$33.90	$33.90
7 purchase totals =	$707.12		$757.2517	$757.25	$757.25	$757.20