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	$47.56	8.204%	$51.4618	$51.46	$51.45	$51.50
Purchase #2	$111.64	8.328%	$120.9374	$120.94	$120.95	$120.90
Purchase #3	$219.40	8.718%	$238.5273	$238.53	$238.55	$238.50
Purchase #4	$182.45	4.422%	$190.5179	$190.52	$190.50	$190.50
Purchase #5	$206.79	8.528%	$224.4251	$224.43	$224.45	$224.40
Purchase #6	$37.32	13.132%	$42.2209	$42.22	$42.20	$42.20
Purchase #7	$219.88	8.557%	$238.6951	$238.70	$238.70	$238.70
7 purchase totals =	$1,025.04		$1,106.7855	$1,106.80	$1,106.80	$1,106.70