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	$189.69	9.826%	$208.3289	$208.33	$208.35	$208.30
Purchase #2	$43.66	6.443%	$46.473	$46.47	$46.45	$46.50
Purchase #3	$53.56	10.305%	$59.0794	$59.08	$59.10	$59.10
Purchase #4	$168.96	3.110%	$174.2147	$174.21	$174.20	$174.20
Purchase #5	$86.70	8.177%	$93.7895	$93.79	$93.80	$93.80
Purchase #6	$144.47	13.668%	$164.2162	$164.22	$164.20	$164.20
Purchase #7	$50.57	4.404%	$52.7971	$52.80	$52.80	$52.80
7 purchase totals =	$737.61		$798.8988	$798.90	$798.90	$798.90