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	$178.49	10.112%	$196.5389	$196.54	$196.55	$196.50
Purchase #2	$131.26	6.529%	$139.83	$139.83	$139.85	$139.80
Purchase #3	$27.45	4.588%	$28.7094	$28.71	$28.70	$28.70
Purchase #4	$168.94	4.237%	$176.098	$176.10	$176.10	$176.10
Purchase #5	$187.95	11.215%	$209.0286	$209.03	$209.05	$209.00
Purchase #6	$121.73	13.782%	$138.5068	$138.51	$138.50	$138.50
Purchase #7	$137.97	10.633%	$152.6404	$152.64	$152.65	$152.60
7 purchase totals =	$953.79		$1,041.3521	$1,041.36	$1,041.40	$1,041.20