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	$41.47	9.173%	$45.274	$45.27	$45.25	$45.30
Purchase #2	$61.60	5.339%	$64.8888	$64.89	$64.90	$64.90
Purchase #3	$68.85	10.818%	$76.2982	$76.30	$76.30	$76.30
Purchase #4	$63.99	10.779%	$70.8875	$70.89	$70.90	$70.90
Purchase #5	$196.41	13.833%	$223.5794	$223.58	$223.60	$223.60
Purchase #6	$196.30	12.276%	$220.3978	$220.40	$220.40	$220.40
Purchase #7	$117.40	12.613%	$132.2077	$132.21	$132.20	$132.20
7 purchase totals =	$746.02		$833.5334	$833.54	$833.55	$833.60