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	$161.59	11.873%	$180.7756	$180.78	$180.80	$180.80
Purchase #2	$110.42	11.798%	$123.4474	$123.45	$123.45	$123.40
Purchase #3	$137.37	7.641%	$147.8664	$147.87	$147.85	$147.90
Purchase #4	$244.70	5.600%	$258.4032	$258.40	$258.40	$258.40
Purchase #5	$62.81	7.575%	$67.5679	$67.57	$67.55	$67.60
Purchase #6	$40.35	10.233%	$44.479	$44.48	$44.50	$44.50
Purchase #7	$186.56	5.308%	$196.4626	$196.46	$196.45	$196.50
7 purchase totals =	$943.80		$1,019.0021	$1,019.01	$1,019.00	$1,019.10