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	$109.72	4.740%	$114.9207	$114.92	$114.90	$114.90
Purchase #2	$128.75	12.501%	$144.845	$144.85	$144.85	$144.80
Purchase #3	$113.56	10.187%	$125.1284	$125.13	$125.15	$125.10
Purchase #4	$117.82	12.694%	$132.7761	$132.78	$132.80	$132.80
Purchase #5	$250.66	3.551%	$259.5609	$259.56	$259.55	$259.60
Purchase #6	$230.88	12.528%	$259.8046	$259.80	$259.80	$259.80
Purchase #7	$103.59	11.511%	$115.5142	$115.51	$115.50	$115.50
7 purchase totals =	$1,054.98		$1,152.5499	$1,152.55	$1,152.55	$1,152.50