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	$179.33	6.180%	$190.4126	$190.41	$190.40	$190.40
Purchase #2	$199.36	3.467%	$206.2718	$206.27	$206.25	$206.30
Purchase #3	$147.41	11.627%	$164.5494	$164.55	$164.55	$164.50
Purchase #4	$193.32	12.135%	$216.7794	$216.78	$216.80	$216.80
Purchase #5	$75.61	9.249%	$82.6032	$82.60	$82.60	$82.60
Purchase #6	$175.86	11.540%	$196.1542	$196.15	$196.15	$196.20
Purchase #7	$103.54	10.765%	$114.6861	$114.69	$114.70	$114.70
7 purchase totals =	$1,074.43		$1,171.4567	$1,171.45	$1,171.45	$1,171.50