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	$174.87	12.617%	$196.9333	$196.93	$196.95	$196.90
Purchase #2	$142.96	12.612%	$160.9901	$160.99	$161.00	$161.00
Purchase #3	$77.91	9.860%	$85.5919	$85.59	$85.60	$85.60
Purchase #4	$77.64	6.638%	$82.7937	$82.79	$82.80	$82.80
Purchase #5	$225.85	10.475%	$249.5078	$249.51	$249.50	$249.50
Purchase #6	$48.49	7.817%	$52.2805	$52.28	$52.30	$52.30
Purchase #7	$148.62	12.564%	$167.2926	$167.29	$167.30	$167.30
7 purchase totals =	$896.34		$995.3899	$995.38	$995.45	$995.40