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	$70.39	11.402%	$78.4159	$78.42	$78.40	$78.40
Purchase #2	$189.75	3.768%	$196.8998	$196.90	$196.90	$196.90
Purchase #3	$166.55	4.319%	$173.7433	$173.74	$173.75	$173.70
Purchase #4	$86.61	12.614%	$97.535	$97.54	$97.55	$97.50
Purchase #5	$36.51	3.527%	$37.7977	$37.80	$37.80	$37.80
Purchase #6	$14.66	9.611%	$16.069	$16.07	$16.05	$16.10
Purchase #7	$149.51	6.178%	$158.7467	$158.75	$158.75	$158.70
7 purchase totals =	$713.98		$759.2074	$759.22	$759.20	$759.10