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	$60.59	3.588%	$62.764	$62.76	$62.75	$62.80
Purchase #2	$102.29	8.657%	$111.1452	$111.15	$111.15	$111.10
Purchase #3	$184.43	6.780%	$196.9344	$196.93	$196.95	$196.90
Purchase #4	$242.42	6.632%	$258.4973	$258.50	$258.50	$258.50
Purchase #5	$212.77	11.128%	$236.447	$236.45	$236.45	$236.40
Purchase #6	$147.75	5.118%	$155.3118	$155.31	$155.30	$155.30
Purchase #7	$170.67	4.788%	$178.8417	$178.84	$178.85	$178.80
7 purchase totals =	$1,120.92		$1,199.9414	$1,199.94	$1,199.95	$1,199.80