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	$204.35	11.802%	$228.4674	$228.47	$228.45	$228.50
Purchase #2	$62.97	12.826%	$71.0465	$71.05	$71.05	$71.00
Purchase #3	$72.33	6.824%	$77.2658	$77.27	$77.25	$77.30
Purchase #4	$233.81	6.606%	$249.2555	$249.26	$249.25	$249.30
Purchase #5	$44.33	3.405%	$45.8394	$45.84	$45.85	$45.80
Purchase #6	$114.88	12.792%	$129.5754	$129.58	$129.60	$129.60
Purchase #7	$243.28	5.130%	$255.7603	$255.76	$255.75	$255.80
7 purchase totals =	$975.95		$1,057.2103	$1,057.23	$1,057.20	$1,057.30