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	$135.90	3.499%	$140.6551	$140.66	$140.65	$140.70
Purchase #2	$47.86	3.681%	$49.6217	$49.62	$49.60	$49.60
Purchase #3	$190.25	5.156%	$200.0593	$200.06	$200.05	$200.10
Purchase #4	$244.54	12.261%	$274.523	$274.52	$274.50	$274.50
Purchase #5	$154.75	8.123%	$167.3203	$167.32	$167.30	$167.30
Purchase #6	$60.62	11.303%	$67.4719	$67.47	$67.45	$67.50
Purchase #7	$204.51	3.589%	$211.8499	$211.85	$211.85	$211.80
7 purchase totals =	$1,038.43		$1,111.5012	$1,111.50	$1,111.40	$1,111.50