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	$127.37	4.527%	$133.136	$133.14	$133.15	$133.10
Purchase #2	$80.26	8.223%	$86.8598	$86.86	$86.85	$86.90
Purchase #3	$223.40	9.423%	$244.451	$244.45	$244.45	$244.50
Purchase #4	$65.57	3.317%	$67.745	$67.75	$67.75	$67.70
Purchase #5	$40.70	10.388%	$44.9279	$44.93	$44.95	$44.90
Purchase #6	$80.33	10.871%	$89.0627	$89.06	$89.05	$89.10
Purchase #7	$100.55	12.813%	$113.4335	$113.43	$113.45	$113.40
7 purchase totals =	$718.18		$779.6159	$779.62	$779.65	$779.60