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	$124.95	13.414%	$141.7108	$141.71	$141.70	$141.70
Purchase #2	$196.33	12.248%	$220.3765	$220.38	$220.40	$220.40
Purchase #3	$123.43	3.357%	$127.5735	$127.57	$127.55	$127.60
Purchase #4	$61.30	3.729%	$63.5859	$63.59	$63.60	$63.60
Purchase #5	$50.90	3.194%	$52.5257	$52.53	$52.55	$52.50
Purchase #6	$45.75	9.535%	$50.1123	$50.11	$50.10	$50.10
Purchase #7	$245.93	3.737%	$255.1204	$255.12	$255.10	$255.10
7 purchase totals =	$848.59		$911.0051	$911.01	$911.00	$911.00