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	$50.95	7.679%	$54.8625	$54.86	$54.85	$54.90
Purchase #2	$118.79	7.595%	$127.8121	$127.81	$127.80	$127.80
Purchase #3	$113.51	10.571%	$125.5091	$125.51	$125.50	$125.50
Purchase #4	$154.91	3.849%	$160.8725	$160.87	$160.85	$160.90
Purchase #5	$27.87	3.689%	$28.8981	$28.90	$28.90	$28.90
Purchase #6	$114.34	8.146%	$123.6541	$123.65	$123.65	$123.70
Purchase #7	$240.32	7.276%	$257.8057	$257.81	$257.80	$257.80
7 purchase totals =	$820.69		$879.4141	$879.41	$879.35	$879.50