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	$142.58	9.318%	$155.8656	$155.87	$155.85	$155.90
Purchase #2	$194.39	4.568%	$203.2697	$203.27	$203.25	$203.30
Purchase #3	$151.47	10.321%	$167.1032	$167.10	$167.10	$167.10
Purchase #4	$155.74	6.826%	$166.3708	$166.37	$166.35	$166.40
Purchase #5	$217.31	3.302%	$224.4856	$224.49	$224.50	$224.50
Purchase #6	$245.63	4.420%	$256.4868	$256.49	$256.50	$256.50
Purchase #7	$54.37	9.278%	$59.4144	$59.41	$59.40	$59.40
7 purchase totals =	$1,161.49		$1,232.9961	$1,233.00	$1,232.95	$1,233.10