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	$216.40	11.638%	$241.5846	$241.58	$241.60	$241.60
Purchase #2	$142.64	5.834%	$150.9616	$150.96	$150.95	$151.00
Purchase #3	$27.67	4.612%	$28.9461	$28.95	$28.95	$28.90
Purchase #4	$167.66	12.477%	$188.5789	$188.58	$188.60	$188.60
Purchase #5	$114.45	4.315%	$119.3885	$119.39	$119.40	$119.40
Purchase #6	$200.25	5.608%	$211.48	$211.48	$211.50	$211.50
Purchase #7	$125.75	11.686%	$140.4451	$140.45	$140.45	$140.40
7 purchase totals =	$994.82		$1,081.3848	$1,081.39	$1,081.45	$1,081.40