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	$183.60	3.836%	$190.6429	$190.64	$190.65	$190.60
Purchase #2	$229.30	7.598%	$246.7222	$246.72	$246.70	$246.70
Purchase #3	$119.72	4.253%	$124.8117	$124.81	$124.80	$124.80
Purchase #4	$128.94	9.401%	$141.0616	$141.06	$141.05	$141.10
Purchase #5	$119.54	9.843%	$131.3063	$131.31	$131.30	$131.30
Purchase #6	$138.88	10.718%	$153.7652	$153.77	$153.75	$153.80
Purchase #7	$136.34	10.258%	$150.3258	$150.33	$150.35	$150.30
7 purchase totals =	$1,056.32		$1,138.6357	$1,138.64	$1,138.60	$1,138.60