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	$169.38	5.520%	$178.7298	$178.73	$178.75	$178.70
Purchase #2	$152.87	9.498%	$167.3896	$167.39	$167.40	$167.40
Purchase #3	$201.85	12.511%	$227.1035	$227.10	$227.10	$227.10
Purchase #4	$168.53	13.471%	$191.2327	$191.23	$191.25	$191.20
Purchase #5	$53.83	5.176%	$56.6162	$56.62	$56.60	$56.60
Purchase #6	$241.59	9.820%	$265.3141	$265.31	$265.30	$265.30
Purchase #7	$163.32	7.461%	$175.5053	$175.51	$175.50	$175.50
7 purchase totals =	$1,151.37		$1,261.8912	$1,261.89	$1,261.90	$1,261.80