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	$176.69	7.612%	$190.1396	$190.14	$190.15	$190.10
Purchase #2	$95.59	8.455%	$103.6721	$103.67	$103.65	$103.70
Purchase #3	$80.81	12.174%	$90.6478	$90.65	$90.65	$90.60
Purchase #4	$59.81	4.127%	$62.2784	$62.28	$62.30	$62.30
Purchase #5	$143.39	8.286%	$155.2713	$155.27	$155.25	$155.30
Purchase #6	$108.95	9.323%	$119.1074	$119.11	$119.10	$119.10
Purchase #7	$89.94	8.311%	$97.4149	$97.41	$97.40	$97.40
7 purchase totals =	$755.18		$818.5315	$818.53	$818.50	$818.50