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	$127.76	10.753%	$141.498	$141.50	$141.50	$141.50
Purchase #2	$240.50	9.669%	$263.7539	$263.75	$263.75	$263.80
Purchase #3	$143.95	10.322%	$158.8085	$158.81	$158.80	$158.80
Purchase #4	$206.51	7.208%	$221.3952	$221.40	$221.40	$221.40
Purchase #5	$72.53	7.767%	$78.1634	$78.16	$78.15	$78.20
Purchase #6	$127.31	3.653%	$131.9606	$131.96	$131.95	$132.00
Purchase #7	$55.95	12.470%	$62.927	$62.93	$62.95	$62.90
7 purchase totals =	$974.51		$1,058.5066	$1,058.51	$1,058.50	$1,058.60