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	$249.28	3.466%	$257.92	$257.92	$257.90	$257.90
Purchase #2	$85.89	11.116%	$95.4375	$95.44	$95.45	$95.40
Purchase #3	$139.72	3.815%	$145.0503	$145.05	$145.05	$145.10
Purchase #4	$201.80	11.710%	$225.4308	$225.43	$225.45	$225.40
Purchase #5	$59.89	5.851%	$63.3942	$63.39	$63.40	$63.40
Purchase #6	$84.32	6.364%	$89.6861	$89.69	$89.70	$89.70
Purchase #7	$221.40	10.841%	$245.402	$245.40	$245.40	$245.40
7 purchase totals =	$1,042.30		$1,122.3209	$1,122.32	$1,122.35	$1,122.30