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	$75.58	7.762%	$81.4465	$81.45	$81.45	$81.40
Purchase #2	$187.74	4.481%	$196.1526	$196.15	$196.15	$196.20
Purchase #3	$42.48	4.517%	$44.3988	$44.40	$44.40	$44.40
Purchase #4	$62.48	13.728%	$71.0573	$71.06	$71.05	$71.10
Purchase #5	$140.98	13.354%	$159.8065	$159.81	$159.80	$159.80
Purchase #6	$132.53	5.407%	$139.6959	$139.70	$139.70	$139.70
Purchase #7	$129.68	3.275%	$133.927	$133.93	$133.95	$133.90
7 purchase totals =	$771.47		$826.4846	$826.50	$826.50	$826.50