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	$41.59	5.316%	$43.8009	$43.80	$43.80	$43.80
Purchase #2	$121.88	10.323%	$134.4617	$134.46	$134.45	$134.50
Purchase #3	$56.58	13.510%	$64.224	$64.22	$64.20	$64.20
Purchase #4	$69.63	3.205%	$71.8616	$71.86	$71.85	$71.90
Purchase #5	$105.36	12.453%	$118.4805	$118.48	$118.50	$118.50
Purchase #6	$207.32	5.797%	$219.3383	$219.34	$219.35	$219.30
Purchase #7	$105.59	13.539%	$119.8858	$119.89	$119.90	$119.90
7 purchase totals =	$707.95		$772.0528	$772.05	$772.05	$772.10