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	$55.86	11.668%	$62.3777	$62.38	$62.40	$62.40
Purchase #2	$31.30	12.749%	$35.2904	$35.29	$35.30	$35.30
Purchase #3	$57.58	3.105%	$59.3679	$59.37	$59.35	$59.40
Purchase #4	$119.83	4.254%	$124.9276	$124.93	$124.95	$124.90
Purchase #5	$58.51	5.726%	$61.8603	$61.86	$61.85	$61.90
Purchase #6	$149.77	12.704%	$168.7968	$168.80	$168.80	$168.80
Purchase #7	$194.44	13.326%	$220.3511	$220.35	$220.35	$220.40
7 purchase totals =	$667.29		$732.9718	$732.98	$733.00	$733.10