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	$94.30	13.521%	$107.0503	$107.05	$107.05	$107.10
Purchase #2	$116.55	9.727%	$127.8868	$127.89	$127.90	$127.90
Purchase #3	$49.36	3.119%	$50.8995	$50.90	$50.90	$50.90
Purchase #4	$56.27	9.463%	$61.5948	$61.59	$61.60	$61.60
Purchase #5	$136.97	4.248%	$142.7885	$142.79	$142.80	$142.80
Purchase #6	$240.38	13.269%	$272.276	$272.28	$272.30	$272.30
Purchase #7	$206.49	4.625%	$216.0402	$216.04	$216.05	$216.00
7 purchase totals =	$900.32		$978.5361	$978.54	$978.60	$978.60