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	$180.93	5.398%	$190.6966	$190.70	$190.70	$190.70
Purchase #2	$72.75	13.398%	$82.497	$82.50	$82.50	$82.50
Purchase #3	$114.90	3.601%	$119.0375	$119.04	$119.05	$119.00
Purchase #4	$123.93	6.361%	$131.8132	$131.81	$131.80	$131.80
Purchase #5	$105.62	9.587%	$115.7458	$115.75	$115.75	$115.70
Purchase #6	$165.82	13.296%	$187.8674	$187.87	$187.85	$187.90
Purchase #7	$194.30	11.641%	$216.9185	$216.92	$216.90	$216.90
7 purchase totals =	$958.25		$1,044.5760	$1,044.59	$1,044.55	$1,044.50