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	$117.87	6.110%	$125.0719	$125.07	$125.05	$125.10
Purchase #2	$6.55	7.689%	$7.0536	$7.05	$7.05	$7.10
Purchase #3	$116.51	6.124%	$123.6451	$123.65	$123.65	$123.60
Purchase #4	$105.34	10.863%	$116.7831	$116.78	$116.80	$116.80
Purchase #5	$181.40	3.400%	$187.5676	$187.57	$187.55	$187.60
Purchase #6	$108.65	13.500%	$123.3178	$123.32	$123.30	$123.30
Purchase #7	$154.33	3.315%	$159.446	$159.45	$159.45	$159.40
7 purchase totals =	$790.65		$842.8851	$842.89	$842.85	$842.90