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	$162.44	13.646%	$184.6066	$184.61	$184.60	$184.60
Purchase #2	$163.34	9.359%	$178.627	$178.63	$178.65	$178.60
Purchase #3	$178.79	12.351%	$200.8724	$200.87	$200.85	$200.90
Purchase #4	$78.25	9.815%	$85.9302	$85.93	$85.95	$85.90
Purchase #5	$39.90	13.103%	$45.1281	$45.13	$45.15	$45.10
Purchase #6	$123.60	12.475%	$139.0191	$139.02	$139.00	$139.00
Purchase #7	$177.94	5.361%	$187.4794	$187.48	$187.50	$187.50
7 purchase totals =	$924.26		$1,021.6628	$1,021.67	$1,021.70	$1,021.60