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	$133.33	7.407%	$143.2058	$143.21	$143.20	$143.20
Purchase #2	$46.47	9.772%	$51.011	$51.01	$51.00	$51.00
Purchase #3	$182.50	7.840%	$196.808	$196.81	$196.80	$196.80
Purchase #4	$228.71	9.649%	$250.7782	$250.78	$250.80	$250.80
Purchase #5	$21.54	13.181%	$24.3792	$24.38	$24.40	$24.40
Purchase #6	$231.84	12.711%	$261.3092	$261.31	$261.30	$261.30
Purchase #7	$109.94	12.108%	$123.2515	$123.25	$123.25	$123.30
7 purchase totals =	$954.33		$1,050.7429	$1,050.75	$1,050.75	$1,050.80