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	$56.78	7.864%	$61.2452	$61.25	$61.25	$61.20
Purchase #2	$184.58	3.699%	$191.4076	$191.41	$191.40	$191.40
Purchase #3	$193.55	11.377%	$215.5702	$215.57	$215.55	$215.60
Purchase #4	$90.96	3.164%	$93.838	$93.84	$93.85	$93.80
Purchase #5	$239.82	11.135%	$266.524	$266.52	$266.50	$266.50
Purchase #6	$144.43	10.485%	$159.5735	$159.57	$159.55	$159.60
Purchase #7	$184.88	12.625%	$208.2211	$208.22	$208.20	$208.20
7 purchase totals =	$1,095.00		$1,196.3796	$1,196.38	$1,196.30	$1,196.30