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	$103.66	10.327%	$114.365	$114.37	$114.35	$114.40
Purchase #2	$55.50	12.523%	$62.4503	$62.45	$62.45	$62.50
Purchase #3	$190.90	5.772%	$201.9187	$201.92	$201.90	$201.90
Purchase #4	$36.33	12.542%	$40.8865	$40.89	$40.90	$40.90
Purchase #5	$231.56	3.786%	$240.3269	$240.33	$240.35	$240.30
Purchase #6	$140.88	13.663%	$160.1284	$160.13	$160.15	$160.10
Purchase #7	$151.77	9.310%	$165.8998	$165.90	$165.90	$165.90
7 purchase totals =	$910.60		$985.9756	$985.99	$986.00	$986.00