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	$101.50	13.654%	$115.3588	$115.36	$115.35	$115.40
Purchase #2	$37.44	13.195%	$42.3802	$42.38	$42.40	$42.40
Purchase #3	$69.71	12.499%	$78.4231	$78.42	$78.40	$78.40
Purchase #4	$158.39	10.269%	$174.6551	$174.66	$174.65	$174.70
Purchase #5	$102.69	4.744%	$107.5616	$107.56	$107.55	$107.60
Purchase #6	$249.43	9.380%	$272.8265	$272.83	$272.85	$272.80
Purchase #7	$231.98	10.512%	$256.3657	$256.37	$256.35	$256.40
7 purchase totals =	$951.14		$1,047.5710	$1,047.58	$1,047.55	$1,047.70