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	$96.77	9.117%	$105.5925	$105.59	$105.60	$105.60
Purchase #2	$49.99	3.818%	$51.8986	$51.90	$51.90	$51.90
Purchase #3	$162.85	11.452%	$181.4996	$181.50	$181.50	$181.50
Purchase #4	$200.87	7.233%	$215.3989	$215.40	$215.40	$215.40
Purchase #5	$125.77	12.874%	$141.9616	$141.96	$141.95	$142.00
Purchase #6	$195.52	9.365%	$213.8304	$213.83	$213.85	$213.80
Purchase #7	$179.94	10.449%	$198.7419	$198.74	$198.75	$198.70
7 purchase totals =	$1,011.71		$1,108.9235	$1,108.92	$1,108.95	$1,108.90