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	$43.95	12.355%	$49.38	$49.38	$49.40	$49.40
Purchase #2	$138.94	9.243%	$151.7822	$151.78	$151.80	$151.80
Purchase #3	$247.60	3.114%	$255.3103	$255.31	$255.30	$255.30
Purchase #4	$72.74	7.502%	$78.197	$78.20	$78.20	$78.20
Purchase #5	$47.77	6.728%	$50.984	$50.98	$51.00	$51.00
Purchase #6	$61.63	8.812%	$67.0608	$67.06	$67.05	$67.10
Purchase #7	$247.80	13.425%	$281.0672	$281.07	$281.05	$281.10
7 purchase totals =	$860.43		$933.7815	$933.78	$933.80	$933.90