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	$119.96	6.314%	$127.5343	$127.53	$127.55	$127.50
Purchase #2	$226.52	6.414%	$241.049	$241.05	$241.05	$241.00
Purchase #3	$158.73	3.724%	$164.6411	$164.64	$164.65	$164.60
Purchase #4	$156.40	5.561%	$165.0974	$165.10	$165.10	$165.10
Purchase #5	$72.54	11.613%	$80.9641	$80.96	$80.95	$81.00
Purchase #6	$159.57	3.252%	$164.7592	$164.76	$164.75	$164.80
Purchase #7	$140.39	10.326%	$154.8867	$154.89	$154.90	$154.90
7 purchase totals =	$1,034.11		$1,098.9318	$1,098.93	$1,098.95	$1,098.90