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	$100.62	4.688%	$105.3371	$105.34	$105.35	$105.30
Purchase #2	$83.37	4.677%	$87.2692	$87.27	$87.25	$87.30
Purchase #3	$99.99	3.160%	$103.1497	$103.15	$103.15	$103.10
Purchase #4	$54.39	3.863%	$56.4911	$56.49	$56.50	$56.50
Purchase #5	$239.59	8.287%	$259.4448	$259.44	$259.45	$259.40
Purchase #6	$131.54	9.497%	$144.0324	$144.03	$144.05	$144.00
Purchase #7	$148.72	9.113%	$162.2729	$162.27	$162.25	$162.30
7 purchase totals =	$858.22		$917.9972	$917.99	$918.00	$917.90