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	$196.35	13.388%	$222.6373	$222.64	$222.65	$222.60
Purchase #2	$155.70	10.330%	$171.7838	$171.78	$171.80	$171.80
Purchase #3	$159.63	3.233%	$164.7908	$164.79	$164.80	$164.80
Purchase #4	$109.94	9.491%	$120.3744	$120.37	$120.35	$120.40
Purchase #5	$99.76	6.524%	$106.2683	$106.27	$106.25	$106.30
Purchase #6	$238.54	8.396%	$258.5678	$258.57	$258.55	$258.60
Purchase #7	$64.64	4.849%	$67.7744	$67.77	$67.75	$67.80
7 purchase totals =	$1,024.56		$1,112.1968	$1,112.19	$1,112.15	$1,112.30