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	$46.46	4.472%	$48.5377	$48.54	$48.55	$48.50
Purchase #2	$250.48	6.393%	$266.4932	$266.49	$266.50	$266.50
Purchase #3	$104.80	4.825%	$109.8566	$109.86	$109.85	$109.90
Purchase #4	$241.80	10.799%	$267.912	$267.91	$267.90	$267.90
Purchase #5	$109.32	3.816%	$113.4917	$113.49	$113.50	$113.50
Purchase #6	$73.86	6.665%	$78.7828	$78.78	$78.80	$78.80
Purchase #7	$114.46	8.717%	$124.4375	$124.44	$124.45	$124.40
7 purchase totals =	$941.18		$1,009.5115	$1,009.51	$1,009.55	$1,009.50