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	$210.52	5.589%	$222.286	$222.29	$222.30	$222.30
Purchase #2	$140.52	7.295%	$150.7709	$150.77	$150.75	$150.80
Purchase #3	$248.50	7.602%	$267.391	$267.39	$267.40	$267.40
Purchase #4	$238.50	6.387%	$253.733	$253.73	$253.75	$253.70
Purchase #5	$29.45	5.109%	$30.9546	$30.95	$30.95	$31.00
Purchase #6	$77.63	6.254%	$82.485	$82.49	$82.50	$82.50
Purchase #7	$44.41	13.118%	$50.2357	$50.24	$50.25	$50.20
7 purchase totals =	$989.53		$1,057.8562	$1,057.86	$1,057.90	$1,057.90