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	$56.99	8.455%	$61.8085	$61.81	$61.80	$61.80
Purchase #2	$48.46	12.458%	$54.4971	$54.50	$54.50	$54.50
Purchase #3	$137.32	3.379%	$141.96	$141.96	$141.95	$142.00
Purchase #4	$59.30	5.790%	$62.7335	$62.73	$62.75	$62.70
Purchase #5	$73.61	6.648%	$78.5036	$78.50	$78.50	$78.50
Purchase #6	$25.25	12.141%	$28.3156	$28.32	$28.30	$28.30
Purchase #7	$243.56	5.398%	$256.7074	$256.71	$256.70	$256.70
7 purchase totals =	$644.49		$684.5257	$684.53	$684.50	$684.50