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	$103.54	8.291%	$112.1245	$112.12	$112.10	$112.10
Purchase #2	$73.75	12.321%	$82.8367	$82.84	$82.85	$82.80
Purchase #3	$182.84	7.369%	$196.3135	$196.31	$196.30	$196.30
Purchase #4	$174.43	9.215%	$190.5037	$190.50	$190.50	$190.50
Purchase #5	$199.80	7.406%	$214.5972	$214.60	$214.60	$214.60
Purchase #6	$114.37	6.409%	$121.7	$121.70	$121.70	$121.70
Purchase #7	$215.98	8.754%	$234.8869	$234.89	$234.90	$234.90
7 purchase totals =	$1,064.71		$1,152.9625	$1,152.96	$1,152.95	$1,152.90