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	$101.30	13.444%	$114.9188	$114.92	$114.90	$114.90
Purchase #2	$182.56	7.811%	$196.8198	$196.82	$196.80	$196.80
Purchase #3	$47.59	8.667%	$51.7146	$51.71	$51.70	$51.70
Purchase #4	$68.85	3.417%	$71.2026	$71.20	$71.20	$71.20
Purchase #5	$27.68	13.412%	$31.3924	$31.39	$31.40	$31.40
Purchase #6	$215.87	4.591%	$225.7806	$225.78	$225.80	$225.80
Purchase #7	$151.95	8.273%	$164.5208	$164.52	$164.50	$164.50
7 purchase totals =	$795.80		$856.3496	$856.34	$856.30	$856.30