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	$232.67	7.329%	$249.7224	$249.72	$249.70	$249.70
Purchase #2	$81.82	9.425%	$89.5315	$89.53	$89.55	$89.50
Purchase #3	$239.81	8.537%	$260.2826	$260.28	$260.30	$260.30
Purchase #4	$57.65	11.149%	$64.0774	$64.08	$64.10	$64.10
Purchase #5	$69.78	5.364%	$73.523	$73.52	$73.50	$73.50
Purchase #6	$82.64	4.580%	$86.4249	$86.42	$86.40	$86.40
Purchase #7	$221.52	8.774%	$240.9562	$240.96	$240.95	$241.00
7 purchase totals =	$985.89		$1,064.5180	$1,064.51	$1,064.50	$1,064.50