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	$200.54	13.135%	$226.8809	$226.88	$226.90	$226.90
Purchase #2	$209.51	12.538%	$235.7784	$235.78	$235.80	$235.80
Purchase #3	$85.42	4.848%	$89.5612	$89.56	$89.55	$89.60
Purchase #4	$37.41	4.440%	$39.071	$39.07	$39.05	$39.10
Purchase #5	$186.96	7.711%	$201.3765	$201.38	$201.40	$201.40
Purchase #6	$120.55	11.760%	$134.7267	$134.73	$134.75	$134.70
Purchase #7	$100.59	3.246%	$103.8552	$103.86	$103.85	$103.90
7 purchase totals =	$940.98		$1,031.2499	$1,031.26	$1,031.30	$1,031.40