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	$133.84	4.123%	$139.3582	$139.36	$139.35	$139.40
Purchase #2	$192.60	7.229%	$206.5231	$206.52	$206.50	$206.50
Purchase #3	$49.38	4.275%	$51.491	$51.49	$51.50	$51.50
Purchase #4	$164.41	13.206%	$186.122	$186.12	$186.10	$186.10
Purchase #5	$144.90	13.713%	$164.7701	$164.77	$164.75	$164.80
Purchase #6	$216.96	3.566%	$224.6968	$224.70	$224.70	$224.70
Purchase #7	$123.45	6.488%	$131.4594	$131.46	$131.45	$131.50
7 purchase totals =	$1,025.54		$1,104.4206	$1,104.42	$1,104.35	$1,104.50