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	$62.86	11.170%	$69.8815	$69.88	$69.90	$69.90
Purchase #2	$212.38	7.509%	$228.3276	$228.33	$228.35	$228.30
Purchase #3	$130.40	9.489%	$142.7737	$142.77	$142.75	$142.80
Purchase #4	$46.64	11.162%	$51.846	$51.85	$51.85	$51.80
Purchase #5	$118.92	3.630%	$123.2368	$123.24	$123.25	$123.20
Purchase #6	$182.66	3.490%	$189.0348	$189.03	$189.05	$189.00
Purchase #7	$179.39	9.569%	$196.5558	$196.56	$196.55	$196.60
7 purchase totals =	$933.25		$1,001.6562	$1,001.66	$1,001.70	$1,001.60