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	$40.52	13.215%	$45.8747	$45.87	$45.85	$45.90
Purchase #2	$36.71	6.431%	$39.0708	$39.07	$39.05	$39.10
Purchase #3	$67.90	7.309%	$72.8628	$72.86	$72.85	$72.90
Purchase #4	$17.34	6.287%	$18.4302	$18.43	$18.45	$18.40
Purchase #5	$234.65	6.360%	$249.5737	$249.57	$249.55	$249.60
Purchase #6	$56.92	13.424%	$64.5609	$64.56	$64.55	$64.60
Purchase #7	$214.42	9.614%	$235.0343	$235.03	$235.05	$235.00
7 purchase totals =	$668.46		$725.4074	$725.39	$725.35	$725.50