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	$124.29	12.245%	$139.5093	$139.51	$139.50	$139.50
Purchase #2	$31.80	5.275%	$33.4775	$33.48	$33.50	$33.50
Purchase #3	$66.26	5.820%	$70.1163	$70.12	$70.10	$70.10
Purchase #4	$213.88	6.440%	$227.6539	$227.65	$227.65	$227.70
Purchase #5	$37.77	5.301%	$39.7722	$39.77	$39.75	$39.80
Purchase #6	$16.54	10.206%	$18.2281	$18.23	$18.25	$18.20
Purchase #7	$76.38	12.139%	$85.6518	$85.65	$85.65	$85.70
7 purchase totals =	$566.92		$614.4091	$614.41	$614.40	$614.50