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	$89.63	7.545%	$96.3926	$96.39	$96.40	$96.40
Purchase #2	$154.82	5.208%	$162.883	$162.88	$162.90	$162.90
Purchase #3	$108.36	5.399%	$114.2104	$114.21	$114.20	$114.20
Purchase #4	$23.83	6.724%	$25.4323	$25.43	$25.45	$25.40
Purchase #5	$128.33	10.748%	$142.1229	$142.12	$142.10	$142.10
Purchase #6	$109.92	12.399%	$123.549	$123.55	$123.55	$123.50
Purchase #7	$121.32	4.311%	$126.5501	$126.55	$126.55	$126.60
7 purchase totals =	$736.21		$791.1403	$791.13	$791.15	$791.10