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	$70.94	10.619%	$78.4731	$78.47	$78.45	$78.50
Purchase #2	$73.78	4.283%	$76.94	$76.94	$76.95	$76.90
Purchase #3	$138.88	13.356%	$157.4288	$157.43	$157.45	$157.40
Purchase #4	$247.74	9.601%	$271.5255	$271.53	$271.55	$271.50
Purchase #5	$225.48	6.646%	$240.4654	$240.47	$240.45	$240.50
Purchase #6	$130.64	4.631%	$136.6899	$136.69	$136.70	$136.70
Purchase #7	$71.95	11.569%	$80.2739	$80.27	$80.25	$80.30
7 purchase totals =	$959.41		$1,041.7966	$1,041.80	$1,041.80	$1,041.80